I generally just translate or compose texts and create words as necessary in transit, adding derived forms as I go. I’ve always thought this approach made the most sense: you get words as you need them, you simultaneously puzzle out any uncertain syntax, you get attestations of all your words, you can incorporate cultural points of interest, and you have the beginnings of a con-literary-tradition.

Otherwise, the old standby Swadesh list and its ilk are standard points to begin from, if not very interesting. As far as plain padding goes, though, it mostly comes down to throwing on affixes and more affixes. I’ve not done much in the way of technical terminology for the same reasons Hallow cites.