Crosswords
Work from the letters you have, or from what the clue means. Both tools work on any grid, from any paper.
Crossword Solver
Type the letters you have and dots for the ones you do not.
Crossword Clue Search
Search a clue and see the answers that have fit it before.
Two ways into the same grid
A crossword gives you two independent kinds of evidence about every answer: what the clue says, and which squares are already filled. The two tools here each work from one of them.
The pattern solver works from the squares. You type one character per square — the letters you have, dots for the ones you do not — and it returns every word of that exact length that fits. This is the stronger of the two whenever you have any crossings at all, because letters are unambiguous in a way clue wording is not.
The clue search works from the wording. It matches what you type against a public-domain definition index and returns the answers those definitions describe. Use it when a corner is completely empty and you have no letters to work with, or when the pattern solver has given you forty candidates and you need to recognise which one the clue is pointing at.
Fill the easy crossings first
This is the whole technique, and it is worth stating plainly: one known letter in a seven-letter answer leaves thousands of candidates, and three known letters usually leaves under twenty. So the fastest route through a hard corner is almost never to attack the hard clue directly — it is to finish the easy answers crossing it, then come back with three letters in hand and read a list you can actually scan.
Count the squares, not the letters
The single most common reason a pattern search comes back empty is a miscount. The pattern length is the answer length, so a dot too many or too few means you are searching for a word that was never there. Count in the grid rather than in your head, and remember that a two-word answer has no square for the space between the words.