For Americans, not much is tougher than saving money. The shortest recorded time in history lasts from the moment you put something by for an emergency to the arrival of that emergency.

But the ''Nervous Nineties'' are ushering in a new respect for money in the bank. A recent poll by Phoenix-Hecht Gallup in Princeton, N.J., found that 70 percent of consumers favor arrangements that, in some way, force them to save.

Automatic-savings systems have been around for a long time. There are payroll-deduction plans run by employers, automatic transfers from checking to savings done by banks and savings and loans, and automatic monthly transfers from bank accounts to mutual funds.

But some interesting new entries are now starting up.

Take the Dollar-for-Dollar program, offered to savers nationwide by Equibank in Pittsburgh. It pays certificate-of-deposit interest rates on deposits of as little as $20 a month.

This program was something of an accident, said spokeswoman Joyce Stump. The bank was researching a new credit product for women when it discovered that credit wasn't the problem. Savings were. The women felt that they were treading water with their 4.75 percent passbook savings accounts (as indeed they were). But they couldn't easily raise the $500 minimum needed for a certificate of deposit.

So Equibank, or its sister bank, Liberty Savings Bank in Philadelphia, will arrange for $20 a month (or more) to be deducted automatically from your checking account. It can deal with virtually any bank or S&L in the country. You pick a savings term (anywhere from seven to 17 years). Your interest rate will then be locked in for the entire term. Today's rate: 7.72 percent, compounded monthly to yield 8 percent. For information, call 800-825-5226.

Equibank's plan isn't for quitters. If you miss three payments in a row, or six payments over the life of the plan, the interest drops to the regular passbook rate. Money withdrawn early also earns interest at the passbook rate.

Providence, R.I.-based Fleet National Bank takes another approach. Its Automatic Savings Plan is a certificate of deposit requiring only a $250 minimum. But after that, you can deposit as little as $50 a month. Current rate on a one-year CD: 7.53 percent.

You will be finding many more banks developing similar plans for regular, $50- or $100-a-month savers. Generally, they assess some sort of penalty for not following through on the savings plan -- usually a drop to passbook rates, but sometimes additional penalties.

An interesting experiment is the new Membership Savings program offered by American Express Co. in nine states and the District. It's expected to be available nationwide by the end of 1991.

Membership Savings is built on the old saw, ''Pay yourself first,'' with just one addition: ''Pay yourself and American Express first.''

As an Amex card holder, you tell American Express how much you want to save each month -- anywhere from $50 to $5,000. When you get your bill, that amount is included. You pay the bill plus your savings deposit with a single check.

Your savings go into a federally insured money-market deposit account that pays 0.5 percentage point over the average rate for such accounts, as tracked by the publication Bank Rate Monitor. Amex recently was offering 6.41 percent, compounded monthly.

Membership Savings levies no fees, requires no minimum account balance and doesn't care if you miss a deposit. For withdrawals, you call a 24-hour toll-free number. The funds will be sent promptly.

For rate-sensitive savers, money-market deposit accounts are not competitive. They're paying 1.6 percentage points less than the average money-market mutual fund.

But if your real-world choice is between an average savings account or no savings at all, that's a no-brainer. Choose the savings.

For the person who can save only $50 a month and who requires ready savings, Amex may actually be the best deal going. The minimum deposit for most bank money-market accounts is $500 and up, and for money-market mutual funds, $1,000 and up. A small saver might build up a savings fund with Amex, then look around for a higher rate.