Your handshake should mean the same thing as a signed contract. If it doesn’t, stop offering your hand.

A verbal agreement has nothing enforcing it, which is the entire point of it. Anyone can sign a contract, since that is a promise with a lawyer attached, but an agreement backed by nothing but you is a direct statement about what your word is worth. People learn which kind you are within about three exchanges. After that, everything you say is priced accordingly.

Before you agree to something quickly, pause long enough to decide whether you will actually do it. Then treat the small ones exactly like the big ones, because there is no separate standard.