What kind of parrot?
The bigger ones should not sit on the shoulder in case they get startled, they could do some damage.
Leave the cage door open and slowly leave their treats out where they'll have to come out and get them.
My cockatiel Jude is sweet and trusting right off the bat but the others needed coaxing.
Once you teach them step up they ought to come out when you want.
Crackers are bad for birds if they have salt.