When words fail you
When you find yourself unable to recall a particular word, there are quite a few alternative filler words you can call on. In English these include thing, thingumy, thingumybob, thingamyjig, wotsit, doobree, doodad, and whatchamacallit. Few of these words have a standard form, so you can spell them how you like.
Knowing the equivalents of these words in other languages is very useful because there will always be gaps in your vocabulary. What kinds of filler words do you use in your language?