Pretty much, there's three ways to make words that I know of.

1. You can take words that already exist to make a word. For example, one of the words I recently made is the English word 'parlay', which is a cumulative series of bets. I combined 'skoz' (to collect/gather/accumulate) and 'dezahrel' (to gamble) to make 'skozahrel'.

2. While the grammer of Dovahzul is based on English, the words are loosely based on the Scandinavian languages (Swedish, Finnish, Norwegian, etc.). Sometimes you can look at the words in those languages and tweak them a bit to make a Dovahzul word. I've also seen other languages, like German or Spanish, used as the basis for a new word, but not very often.

3. If all else fails, just make something up. The words I made for 'left' and 'right', 'vahlt' and 'volt' aren't based on anything, I just thought of random sounds and looked to see if they existed already, and they didn't.

One way I've thought of new words is by looking at liscence plates and trying to pronounce them. It helps that in my area liscence plates have a letter-letter-letter-space-number-number-number format, though.

Of course, I always forget them when I get home...

There are many ways to make a word. Sometimes I look at another dovah word, and see any thing that is comparable for an English word for use to make a dovah word. Or, like shy night said, just make up a do ah sounding word