AFTER WEEKS of preparation, it's finally time to leave for New York City and the Democratic National Convention. It's still difficult to believe I'm going, for this is something I've wanted to do for 20 years.

Ever since the caucus that elected the delegates and alternates, there have been questions from the wire services, national magazines, television and radio stations and local newspapes. The questions aren't terribly original: How am I pledged? Do I favor an "open" convention? How would I vote if the convention were open? Who is my second choice if President Carter isn't able to get the votes?

Of course, the big question is, "Are you a delegate or alternate?" Just saying I'm an alternate is enough to stop most of the other questions. The fact that I'm an alternate by only three or few votes doesn't matter.

Alternates don't get invited to the White House. Alternates don't get special buttons. Alternates don't get nearly as much mail or lobbying.

The train leaves from New Carrollton. I love trains, and it's my first train trip in three years. For some of the delegation, it's the first time in 50 years. Because there is concern about protesters at Penn Station, we change to buses at Newark for the last leg into Manhattan.

Confusion reigns as 100 people, give or take a few, try to register at the same time. Luggage is left on the sidewalk, lines are long and tempers are short.

There's only time for a short caucus meeting, where we learn of other upcoming meetings, before we get to go to dinner. The Carter delegates have to return by 9 p.m. for still another meeting. Half the delegation spends the rest of the evening in the Maryland hospitality suite or elsewhere, and the other half goes to sleep, aware of the demands on the mind and body within the next few days. Monday

We have to pick up daily credentials at 7 a.m., so the day starts early. Some may have come to New York to play, but for those who are serious about this convention, there's a lot of work and a lot of reading. There's also a lot of waiting.

The convention is recessed from 5:30 to 6:30 p.m. because things were moving too swiftly and promises were made about prime time coverage. However, at 6 p.m. there's suddenly a loud commotion from the floor and gallery, apparently stirred up by the networks as they open their newscasts. This is definitely a media event. There's a feeling we'll need that hour later this evening and many wish we could go on to other business. But we wait.

The Garden seats 40,000 for other events, twice the capacity of the Capital Centre, but it still is much smaller than I imagined. Again the magic of media has made things larger than life. The crush of people is ever-present, especially when compared to the plush open surroundings enjoyed by Walter Cronkite and Frank Reynolds.

Minolta cameras have been distributed to delegates and alternates, and a prize awaits the best photographs. Everyone is looking for that unique shot. Hometown television crews are also, so the people with the unusual hat, T-shirt or collection of buttons, or bare feet or sign is sure to get plenty of attention. Women are warned about crossing their legs, and are cautioned about using handkerchiefs.

Finally, the Monday night show starts. No one really expects either Carter or Kennedy delegates to change their minds about changing the convention rules midstream, but the speeches are interesting and the computers, calculators and tally sheets are evident everywhere.

If I ever attend another convention, I'll be sure to bring a portable radio or television. What we don't have is the state-by-state breakdown of the Carter and Kennedy delegates, so we can't really tell if there is any deviation. The result is obvious almost from the beginning, but when New York and other large delegation states pass, the suspense mounts.

Those who leave after the talley are greeted by sheets of rain. There are buses to return us to our hotels, designated as orange, red and green lines. Someone from the transportation committee is yelling, "Orange to the right, red and green to the left, and lightning and thunder from above." The rain smells good even if the body is soaked totally.

I can't believe we've only been here one day. Tuesday

More meetings and more caucuses. It's 7 a.m. for credientials pickup again and most did not get to sleep until 1:30 or later.

Esther Coopersmith has arranged for Danish and coffee at the U.S. mission to the United Nations and conversation with Ambassador Donald McHenry. There are conflicting caucuses, but suddenly there's an advantage to being an alternate. My delegate and I agree on most issues, so I can trust her to vote as I would if I were on the floor.

Back at the Garden, the minority reports have started, but there's a phone tally instead of a roll call. It's supposed to be faster , but there's a gap between theory and practice.

While the phone tally is being taken, the knitting, crocheting, card playing, etc., continues. There's no reason to leave the Garden, for it takes too long to get in and out. The shuttle buses we were told would be operating all day long don't, so it's up to public transportation if you're to return to the hotel for a bite to eat or a change of clothes. The complimentary copies of Newsweek the alternates are supposed to receive never arrive, so it's back to campaign literature or the directory of delegates.

We're certain the media have come to New York because there's so little happening back home in August. But this morning we've learned Prince George's County employes have gone on strike and suddenly we who are the center of attention are craving news from back home. It's easy to get a copy of the paper, but there's not enough news to satisfy our interest.

I'd like to be on the floor to vote on the minority reports on the economic and jobs issues. But too many carbonated drinks or a bad milkshake leave me sick, and I limp back to the hotel and bed for an hour. It's little comfort to know a deal has been arranged and I wouldn't have been able to cast an individual vote if I'd been allowed to.

There's a four-state party among the delegates from Puerto Rico, Maryland, Iowa and Nebraska, with Pina Coladas, crabs and crab balls, ham and cheese. But everyone has invited everyone and the early arrivers take to the food as though it were dinner instead of a midnight snack. It's 2 a.m. before even the earliest departers are in bed, and much later for some others. It's been a long day. Wednesday

Credentials at 7 a.m. agains. Sen. Conroy has provided our first real breakfast, complete with champagne, and last night's Kennedy speech is the main topic of conversation. For those who aren't hoarse from all the screaming and yelling last night, there's a grand feeling that the Maryland delegation, despite some animosity over the last few weeks, is enjoying a very harmonious relationship, unlike some other states. We have worked well together in arrangements, fund raising and other campaigns, and there's a confident feeling that we'll be working well together again for a victory in November.

Fortunately, the convention isn't called until noon today, so those who aren't going to more meetings and caucuses have a change to catch a little shut-eye.

There have been hundreds of things to do, all arranged by the convention committee, from sightseeing to theater tickets. But most of us have had little free time. It's been years since I've attended a Broadway show, so that was my choice of entertainment. The check was mailed in weeks ago, and "Evita" is everything I heard it would be.

Back at the Garden the business continues. Alternates have one consolation. We're up higher, so we can see the speakers better. The air conditioning works better, and there isn't the crush of lobbying and media to block the aisles. We can also see the large movie screens more easily, yet we don't really lose the flavor or excitement of the moment's activity. It's almost a pleasant compromise.

People who've attended previous conventions say this one doesn't have the excitement or pizzazz of the others they've seen. As a first-timer, I can't tell. I feel an energy and a sense of history. Of the 18 people in our Prince George's contingent, only one has ever been a delegate before.

The frenzy of the presidential roll call is exhausting, and I'm pleased to be sleeping by 2 a.m. Thursday

Credentials aren't available until 10 today, and the session doesn't start until 5. Since the real business won't begin until 9 or 10 p.m., there is finally plenty of time for signtseeing and shopping. The Hayden Planetarium isn't nearly as good as I thought it would be.

The week has taken its toll, with shinsplints, blisters and calluses from walking the sidewalks of New York. As the vice president and president finish their speeches, the crowd presses closer, shouting, cheering, popping balloons and throwing confetti. Suddenly I realize I'm close to fainting. Space is cleared, a chair is found and the attendants at the emergency medical booth are competent and friendly. I have missed the introductions of dignitaries on the stage, but I get to see some of them and the president as they walk past my sick bay on their way out of the Garden.

It's been quite a week. A fifth wheel is more useful than an alternate. But if I ever get the change, I'd do it again.