1. Monday is the easiest puzzle day, Saturday is the hardest.
Most people assume the iconic Sunday NYT puzzle is the most challenging, but most crossword enthusiasts find Saturday's puzzles have the highest level of difficulty.
The puzzles start gentle on Mondays and get increasingly tougher as the week goes on, so if you're a novice, start with a Monday puzzle and work your way up to a later-week puzzle. (You can buy books of puzzles from certain days of the week; here's a book of all-Mondays.)
2. Figure out the annoying (but sometimes clever!) gimmick.
Most Sunday puzzles, and some weekday puzzles, have a "theme" that can be a bitch to figure out, but put you on the fast track to Solvesville once you get it.
For example, this Sunday's puzzle was called "Downright Tricky!" Each "gimmick" answer ran down and then traveled to the right. The reason is explained in the clue for EL CID ("Spanish hero whose 113-Down is represented enigmatically six times in this puzzle"). In other words, the theme answers form six "L"s, and all the "L"s are three-part phrases where each part begins with "C," "I," and "D," respectively.
Yeah, they're a pain. But once you figure out what the puzzle is doing, you'll be able to easily fill the remaining clues in the theme.
3. Tenses will always match up.
4. Take a break if you get frustrated.
Sometimes putting a puzzle down and walking away from it is the best thing to do when you're stumped. Later, pick it up with a fresh set of eyes, and you'll be surprised how much you can solve!
5. A question mark at the end of the clue means it's going to be a pain in the ass.
Well, it means the answer is going to be some sort of pun or wordplay. Some examples from a recent Sunday puzzle:
Eye covers for the naive? --> WOOL
Circular parts? ---> ADS
Pot pusher's vehicle ---> TEACART
Remember, the Times has a reputation for being a wee bit stodgy. So think dad humor, not Jon Stewart humor.
6. Beware of homonyms.
7. If you're stumped on one single letter, try every letter of the alphabet until you get it right.
8. If there's an abbreviation in the clue, there will be an abbreviation in the answer.
For example, this clue uses "org." as an abbreviation for "organization," so the answer would rarely be "NATIONAL HOCKEY LEAGUE." Instead, it's "NHL."