I usually stamp my packages with various denominations of stamps to get the right amount.  Most books are over 13 oz, so I need to take them into the post office.

I have several different post offices near me and each is different:

Post Office 1:  There is one counter with a surveillance camera installed and anyone can just drop off stamped packages without needing human interaction

Post Office 2 and 3:  I can jump the line and when the clerk is finished with the current patrol I say "These are ready to go" and hand them over

Post Office 4:  I ask "Can I just give this to you?".. and she says "Oh No!, you need to wait in line".  When I got to her after waiting behind the other folks, she then weighted the package and got out her calculator and added up the stamps to check.  Then she said it was fine.  

I was just wondering if the first 3 post offices were just being "nice" or if they were skirting rules.  I avoid Post Office 4 when possible. 

Yes the first 3 post offices are just being nice and skirting the rules. The rule is it is to be a hand to hand exchange and "the questions" have to be asked..you know, anything liquid, fragile, perishable of hazardous.

When I was using stamps, my PO was similar to your options 2 & 3.  I would stand off to the side and wait to catch a clerks eye, then hold up the package with postage visible, and wait for someone to get free and wave me over.  To be fair, they would usually ask the required questions, then I would 'pass the package over the counter.'  If I was sure of postage, I didn't wait in line and the clerks didn't ask me to...same as customers just picking up mail do not have to wait in line.

Now I usually buy counter postage (and watch them scan my PBS DC), fortunately we don't always have a line, and usually short if there happens to be one.

I have an AWESOME post office.

When I go to the PO and step up to the counter, I immediately say, "Nothing liquid, fragile, perishable of hazardous" (which at this point usually gets a smaile because they know me!).  But even if I say, "Nothing extra on any of them," they ask about DC, etc.  I guess they have to.

Interesing and helpful... Thanks!  I will still avoid post office #4  but if 1,2 or 3 ever ask for me to do a something extra I will do it gladly :  )