On St. Patrick's Day, House Speaker Thomas P. (Tip) O'Neill handed reporters lapel pins with Irish and American flags crossed in friendship. "The top of the mornin' to ya." he said, opening his daily press conference.

The reporters laughed but said nothing. "You can tell there's not an Irishman in the crowd." O'Neil grumbled. "You're supposed to say, 'And the rest of the day to you.'"

It was all in good-humored fun. The laughter O'Neill drew that morning was no unusual. He's a funny, outspoken man. He loves to tell stories and he's good at it. And, for the first time in years, a speaker's press conference has become a place where reporters can really find out what House Democrats are up to.

Tip O'Neill wears the speakership like a glove. He and the office were meant for each other. He's had his eye on it since he came to Congress 24 years ago. He trained for it in Massachusetts as an all-powerful speaker of the state legislature at age 36. And now he has it.

When Rep. Sam Gibbsons (D-Fla.) ran briefly against O'Neill for majority leader 4 1/2 years ago and then withdrew for lack of votes, he told the House Democratic Caucus: "Tip O'Neill has no enemies in his House."

Rep. Richard Bolling (D-Mo.), urbane scholar of the House, said: "Tip can do things with people that a lot of us can't. It must be something Irish, I guess."

O'Neill succeeded John F. Kennedy in the House. Though his constituency includes Harvard and the Massachusetts Institute of Technology, this grandson of a County Cork bricklayer went to Boston College, a Catholic schools, and built an insurance business before going to Congress.

O'Neill stands 6 foot 3 under a shock of white hair and his weight alides up and down between 230 and 288 pounds. It was 235 last week. He boasts that he has lost 1,000 pounds over the years. Until he became speaker in January, his wife MIllie and their five children stayed in the big old house in North Cambridge, Mass., in the neighborhood where he was born 64 years ago. They moved, into a condominium apartment here last month.

For all those years, O'Neill shared a one-bedroom Washington apartment with Rep. Edward P. Boland (D-Mass.) who came to Congress with him. They never cooked a meal in the place, says Boland. They ate a lot at downtown steakhouses. Their refrigerator was filled with cigars and Tip's diet soft drinks.

O'Neill knows the raw power he wielded in Boston 25 years ago won't work with today's Congress of educated independent young people. he operates through forceful persuasion and commands respect as a shrewd politician with sensitive antennae for reading the House. He is straight-forward and candid. If he's upset, he lets you know and doesn't carry a grudge. He is a very partisan Democrat and a big earthy Irishman with a happy face.

It's still early. The toughest issue - energy - lies ahead. But in less than three months he has shown more of the take-charge leadership expected of the top man in the House than any speaker since Sam Rayburn in his prime 20 years ago.

He got a minus from many members for his support of Rep. Robert L. F. Sikes (D-Fla.) who was stripped of a subcommittee chairmanship in January after being reprimanded by the House last year for a conflict of interest. O'Neill, who is not close to Sikes, called it double jeopardy and said he would have voted to dump Sikes last year had it been recommended then.

Labor lost a big one in the House defeat of the common site picketing bill. O'Neill accepted that as a defeat for the House leadership because he considers organized labor a part of the Democratic Party. But it was not an administration bill, had a narrow constituency and O'Neill had warned labor they didn't have the votes. The outcome was not considered a serious setback for O'Neill.

But on the two big issues the House has dealt with this year - the economy and ethics - O'Neill is credited with highly skillful performances by his Democratic colleagues.

Presiden Carter's economic stimulus package moved easily through the House. Increased here and there at the request of the Democratic leadership. When the House Appropriations Committee rejected an extra $1 billion for jobs that the House Budget Committee had approved. O'Neill called in appropriations Committee elders and "gently nudged them," according to one who was present, into offering amendments to add the $1 billion on the House floor.

"We could have crammed it down their throats," said Majority Leader Jim Wright (D-Tex.), "but it was better" for the Appropriations Committee to do it.

O'Neill said the other day he has put "more money into the federal budget without offering amendments" than any other member in the last 20 years.

As an example of how he operates, O'Neill said that when he heard a few years ago that the Appropriations Committee was about to cut back cancer research, he called in half a dozen cancer specialists, sat them down with committee members and a $160 million cut was averted.

O'Neill has drawn widest admiration for holding together and pushing through the House the "toughest" ethics code for members which was his earliest pledge after the Wayne Hays sex-payroll scandal of last year.

The code was in potential trouble in the House Administration and Rules committees, which had jurisdiction over parts of it. O'Neill kept both committees in line and made a forceful floor speech just before the overwhelming vote approving it. O'Neill took the heat for the congressional pay raise which members got without voting on it and he reminded them the ethics code was the second part of the deal.

At least three Democrats on the Rules Committee were threatening to balk at the limit on outside income because of their lucrative law practices and speaking fees. On Ash Wednesday, O'Neill held a breakfast in one of his Capitol hideaways for the 11 Rules Committee Democrats and when the vote came they were with him unanimously.

There was no strong-arm stuff, said those who were present. O'Neill said he needed their support, that the code was important to the party, that his reputation was at stake. He reminded them they were his handpicked people. The only committee assignments made by the speaker are the Democrats on Rules, to assure their faithful performance as an arm of the leadership.

"He's an Irish politician," says Bolling, a senior Rules Committee member. "No table pounder. He puts an arm around your shoulder and says he needs you . . . When he's going somewhere, he's like a tank, a kind of tank."

O'Neill got on the leadership ladder by accident six years ago after John W. McCormack, whose Boston district adjoined O'Neills, retired as speaker. Carl Albert moved up to speaker and Hale Boggs to majority leader, and the position of majority whip was open.

Boggs wanted Rep. Dan Rostenkowski (D-Ill.) as his whip, but Albert exercised his veto because the Illinois delegation had not turned in cards pledging support for Albert's election as speaker as other states had done - at O'Neill's suggestion. Boggs then picked O'Neill, who moved up to majority leader when Boggs was lost in a plane in Alaska two years later and then to speaker when Albert retired in January. He is presiding officer of the House and leader of the majority party, a position usually considered the second most powerful in the federal government.

McCormack and Albert were "more coordinators and schedulers" than strong leaders, said Rep. Morris K. Udall (D-Ariz.), who has run for majority leader, speaker and president. "But Tip came out of the Massachusetts legislature with a tradition of strong speakers. He is a perfect bridge between the young and the old, comfortable with both."

O'Neill can act like a fellow with one foot still in the good old boy club supporting Sikes ("loyalty," said an aide), and at the same time lead the charge for reform and be the only member of the party leadership voting against U.S. involvement in the Vietnam war.

Rep. Phillip Burton (D-Calif.), a tough activist who fell one vote short of becoming O'Neill's majority leader - to O'Neill's relief - said O'Neill is "making tough decisions and putting the prestige of his office into getting things done, which is what a speaker is supposed to do."

The speaker doesn't preside when the House sits as a committee of the whole to debate bills. But O'Neill spends a lot of time on the floor, available to members. "You can go over and talk with him," said Rep. Bob Carr (D-Mich.), a second-termer, "and that means a lot." Two years ago, Carr was telling Albert he wasn't a leader and should step down. Recently he sent O'Neill a note of thanks for putting through the ethics code. "A decided improvement," said Carr.

A staff person who wished to remain unidentified expressed admiration for what O'Neill has accomplished but expressed reservations about his style. He said procedural change has given the speaker more power than any has had since the revolt again "Czar" Joseph Cannon 65 years ago and that O'Neill, with his background, might try to restore one-man rule or cut deals and "to get one thing, give away the store."