1995 Nissan Maxima Wont start

First of all. Who told you it's either the starter or the relay?

Most common 3 things when a car doesn't start. Maybe you have a dead battery or it could be a weak alternator that's about to die or just a dead starter.

1) dead battery
2) alternator almost dead
3) starter

Sometimes a car doesn't start because the spark plugs are too old and needs to be replaced. Normal spark plugs are good for 50,000 km or 31,000 miles
eg. Start replacing it at 45,000 km or 28,000 miles

Platinum spark plugs are good for 100,000 km or 62,000 miles. Start replacing it at 59,000 miles

(rare) sometimes a car doesn't start because of a clogged fuel injector or faulty fuel pump/dead fuel pump.

When your car doesn't start. What kind of noise do you hear when you turn the keys? Or no noise?