I tip 10% on take out when we are ordering multiple items that need to be packaged individually- like at a Mexican restaurant where they are bagging chips, putting salsa in containers, separating out the refried beans from the rest of the meal, etc. Or at Wildflower where everything is packaged individually and placed neatly in a bag. The hard reality here is that the people packaging to go items are not usually the servers- they are kitchen employees- and probably see none of this tip. If they are just throwing a pizza in a box and taking payment no way I am tipping. A tip is for effort/good service- putting a pizza in a box and handing it to me doesn't qualify.
For table service a minimum of 20% pre tax, since the server isn't serving me tax. DW used to wait tables, so for exceptional service we will often do 25-30%.
Buffets are 10-15% everywhere except Disney since they add in the gratuity there.