New credit and hard inquiries (10%)

A hard inquiry is recorded when you apply for credit. One costs a few points and fades within a year. Several in a short window looks like distress and can trigger denials.

Rate shopping for one car loan or mortgage is treated differently: applications of the same type within about 14 to 45 days count as a single inquiry. Do that comparison in one short stretch.

Checking your own score, or a prequalification that says 'soft pull', does not affect anything.