For Northern Virginians who wonder whether actions taken by the state legislature really affect their lives, some answers will be found at the gasoline pump, in food and drug stores, and in state income tax forms.

Those are only a few of many areas where decisions made in this year's 60-day session of the General Assembly could have impact on the pocketbooks of the average Northern Virginia family, and according to area lawmakers, most of the economic impact will be negative.

"It's been a bad session for the average taxpayer," conceded Fairfax Sen. Richard L. Saslaw.

Gasoline prices in Northern Virginia will likely be at least a nickel higher July 1, not because of overseas oil sheiks but because of two highly controversial bills enacted here.

Two cents will come from a statewide tax increase to pay for roadways.The rest will come from a 2-percent gasoline tax increase imposed solely on Northern Virginia to pay for the Metro rapid transit system.

Losers in the General Assembly were most of the major tax reduction measures that would have added to family incomes. Families will still be paying the 4 percent sales tax on food and nonprescription drugs. Bills to repeat both taxes died in committee. So did that would have substantially lowered state income taxes by tying family exemptions and credits to the inflation rate.

About the only tax reduction measure that passed was repeal of the 4 percent state sales tax on fuel oil, firewood and other home heating fuels, but even its impact won't be felt until July 1982, because sponsor Erwin S. Solomon (D-Bath) reluctantly agreed to delay the bill's effective date until then in order to keep it from being killed.

While the Assembly was reluctant to reduce the taxes paid by families, it was more benevolent when it came to the state's banking institutions. One bill that breezed through allows credit unions to raise the annual interest ceiling on loans from 12 to 15 percent. Another allows savings and loan associations to slap a two dollar monthly fee on dormant savings accounts.

Yet another measure removes the state-imposed ceiling of 12 percent on second mortgage loans with a maturity period of 10 years or longer, meaining borrowers will pay more. A bill to remove the interest limit on home improvement loans, currently at 14 percent annually also cleared both houses.

For families thinking of buying a new house, the most important bill was one that permits lending institutions to issue mortgages at varialbe interest rates. Banks and savings loans can renegotiate mortgages every three to five years and change the interest as much as 5 percent annually and 5 percent for the life of the mortgage.

The bill was opposed by consumer advocates but easily passed both legislative houses here after intensive lobbying by the Virginia Savings and Loan League.

The legislators were less generous when it came to consumers fighting against banks. A bill sponsored by Prince William County Sen. Charles Colgan to allow customers who are victims of banking errors to collect the same $7 to $10 fee that banks collect when a customer makes a mistake passed the Senate it later died in a House committee dominated by legislators with economic ties to the banking industry.

The bill that lawmakers say most affects the average Northern Virginia residents is the Metro sales tax, which will add 2 percent to retail gasoline prices this July and another 2 percent two years from now. In return, the bill is designed to give some relief to local taxpayers who presently fund the entire system through their property taxes.

Del. Martin H. Perper (R.-fairfax) estimated that by the time the full 4 percent tax is phased, in Fairfax homeowners could save at least $80 a year in property taxes. But other legislators contend the property tax reduction will never occur because local government will find other uses for the money.

"It's just a mirage," says Del. Vincent F. Callahan (R-Fairfax).

One other measure that affects motorists is a bill requiring annual pollution inspections of automobiles in the region. The Environmental Protection Agency coerced the legislature into passing the bill by threatening to withhold more than $100 million in federal funds.

For most motorists, the requirement may result in small charges for carburetor adjustments, plus $3.50 for the inspections. But a few may face up to $75 worth of repairs to the clean air equipment in their cars.

For Northern Virginia tenants, the Assembly approved a bill raising the amount of interest paid on security deposits from 3 to 4 percent. It also extended to six months the present 90-day limit on notice given to tenants threatened by condominium conversion of their apartment buildings. But a bill that would have given tenants' groups the same rights to buy their buildings as tenants in Maryland and the District have was defeated in committee.

Most of the measures that would have affected relationships within families died. Chief among them was a divorce law reform bill that would have set up additional guidelines for judges dividing marital property. Another bill to lower the required one-year legal separation period for divorce to six months also failed.

The legislature even delved briefly into the bedroom with a bill that would have legalized oral and anal sexual acts between consenting adults of the opposite sex, and would have downgraded homosexual acts from a felony to a misdemeanor. The bill passed the House but died in a Senate committee.

Finally, a bill that would have required periodic status reports on the impact of state programs on families was killed by lawmakers who feared it would hurt families more than help them.