Start the vehicle, center the steering wheel and secure the wheel.
Now look down the inside of the front tire edges as you would a gunsite, you should see some of the back tire which would mean you have toe in. If can't see any of the back the tire the wheel is toed far out.
Check both so you have a good idea which is the problem wheel before your measurements. Now take a tape a measure from one wheel to the other using the tread as your mark, do this from the front and back of the tire making sure you use the same tread mark from side to side do this for front and back.
Ok front wheel drive cars should be toed out /16, due to the power wanting to suck the tires inward. Rear wheel drive toed in a /16 because the power wants to push the tires outward.
So say your front measurement is 42 13/16ths and your rear is 42 3/4 the front tires are toed out a 16th which is optimal for a front wheel drive. This applies if linkage and chassis parts are in working order. Your measurments will differ and adjustments can be made via tierod (with front tires off the ground) Sorry forgot to mention, lower vehicle before measurments are made.
Toe is one aspect of an alignment which can be checked at home, a sawtooth wear pattern would indicate a toe problem, as a beveled wear points to camber problems