Q On what day of the week do most outfits change their interest rates? A Savings rates typically change on Tuesday or Wednesday, after institutions have studied the results of Monday's Treasury-bill auction. That tells them which way the wind is blowing. Mortgage rates, on the other hand, can fluctuate every day, depending on world events ranging from oil prices to Clinton catching cold. Personal loan rates are apt to change only once or twice a month, and credit cards just one time in a year.

Q What are some of the biggest behind-the-scenes financing tricks to be leery of when you buy a new car? A For openers, steer clear of: Back-end extras such as credit life insurance; dealer retention rates where the dealer works out an 8 percent rate with the bank, but charges you 9 percent; and buy-down rates where the dealer pays the wholesaler a few hundred dollars to bring the advertised rate down, but that amount gets added to the price of the car.

Q On average, where do you find the highest savings yields and the cheapest loan rates? A First, savings: Thrifts on average pay a quarter of a percentage point more than banks; credit unions might pay three-quarters of a point more, depending on the type of account.

Institutions in the largest metropolitan areas such as New York, Los Angeles and Chicago tend to pay less than cities the size of Cincinnati, Milwaukee and Seattle, according to Bank Rate Monitor.

On loans, the only account where banks offer cheaper rates is on home equity lines of credit - 7.02 percent vs. the 7.48 percent charged by thrifts. The latter narrowly beat banks on new car loans (8.74 percent vs. 8.85 percent) and credit cards (18.16 percent vs. 18.37 percent).

Q Where can you find the lowest fees on ATM (automated teller machine) transactions? A At thrifts and small banks. Because they don't offer ATMs on every street corner like the big banks do, they make up for it in lower fees.

Q Where are the best and worst places to borrow in the United States? A For mortgages, move to Washington, D.C. The average 30-year fixed-rate loan is 7.36 percent, while the typical first-year rate on an adjustable-rate mortgage is 4.19 percent. On Feb. 16, for example, NationsBank's ARM rate was only 3.75 percent in D.C., Houston and Dallas.

Rip-off state No. 1: California, where you pay an average of 19.69 percent on credit cards, and 17.92 percent on unsecured personal loans, but earn a measly 1.57 percent on your checking account.

Q Which type of loan could zing you the most in future years - an ARM or a home equity line of credit? A The equity line. Although the rate is generally tied to the banks' prime rate, the life-of-loan cap can soar as high as 24 percent in some states. By contrast, an ARM rate is usually capped at 6 percent above the first-year rate. Based on the current average of 4.72 percent, your rate wouldn't go above 10.72 percent.

Q Name one way banks can extract an extra fee if you open a home equity credit line, but never use a dime of the money. A Many charge an "inactivity fee" of between $100 and $150 a year if you don't touch your funds.

Q On what kinds of accounts might you be able to negotiate your rate with a bank? A Not every outfit will wheel and deal, but try: a) getting the annual fee waived and the rate reduced on credit cards; b) having the rate dropped half a percentage point on auto loans; and c) squeezing out an eighth to a quarter of a point more on $100,000 jumbo certificates of deposit.

Q Of all the things banks sell you, on which one do they enjoy one of their biggest markups? A On checkbook reorders, believe it or not. You can pocket the profit yourself by buying personalized checks elsewhere.

Robert Heady's syndicated column appears Tuesdays in The Seattle Times. Heady is editor and publisher of four banking publications.