Form 4 needs to have all the info on it, LEO's won't sign blank forms (two copies have to be signed). Just go in neat & tidy and tell him what it is that you are buying, why you are buying it (so you can target practice without alarming the neighbors, you want to target practice or teach your kids- student's without hearing protection so they can hear your instructions etc.) You'll likely have to leave the forms and pick them up after they run you thru FDLE. Be sure that the info in the CLEO line is completed, agency, CLEO's title (sheriff, state attny), name typed, agency phone number. Email or IM me if you need help.
--C
Edited to add, your dealer should have given you everything completed & typed, requiring you to obtain only the prints, photos and sigs, that what I do for my buyers. If it's a private sale, you can go to titleii.com and do the Form 4 online and print two copies. Get the private sellers F4 and copy the firearm data EXACTLY as it appears on the F4.