First of all, this site can be used as a basic kanji dictionary. Enter the kanji into the search box and press return, then click on it again, and you'll be taken to its translation. More interestingly though, it can also be used to find a kanji which you don't know how to type in. Here's how it works.
Suppose you ran into the kanji 動, which you hadn't seen before. It looks a lot like one you do know, 働 from 働く hataraku "to work". If you enter 働 as query, the search display will show you a number of kanji which look similar. Searching this way, you can quickly find the unknown kanji you want.
If you enter a query, and can't immediately see the kanji you're looking for in the results, you should click on the next closest match. By doing this a few times, you should hopefully find your target kanji.
Whilst this form of search is designed for single-kanji queries, you can also use it for words by querying any of the kanji in the word. When you find your target, its translation page provides single-click queries to word-level dictionaries.
Whilst searching this way can be fun, it's not appropriate all the time. You might not know any similar kanji to the one you're trying to find, or you might just have a difficult one. The best strategy in general is to have a number of dictionaries you can use, and to pick the best one for the job. We recommend:
Visual kanji search (r77:6a5ee62368d6)