One of the most stressful things about field work is that you have a limited amount of time and an unlimited number of things you want to ask. Often you end up with so much more data than you can ever analyse, but sometimes it's not until you get home that you realise that no matter how comprehensive you've tried to be there are things you've forgotten to get.
One of the things I seem to generally forget is to make sure that I get the negative equivalent for some constructions. so while I have lots of 'let's do X' and 'I want Y' I don't have a lot of 'let's not do x' and 'I don't want Y.' I also can;t find a decently set out di-trasitive paradigm (X gave Y Z).
I'm sure that all these things are possibly buried deep in notebooks, especially from some of the older sessions when I wasn't as up to speed on databasing all the utterances I collected. Still, it's learning these things that make me more competent every trip. It's just annoying on a Friday when I just want to finish writing this chapter section.