1. Learn all of the 2 letter words and as many of the 3 letter words as you can. You can find them at this link
2. Never waste 's' tiles. Unless you have like 3 of them in your rack, are bridging off another word, or are reaching a double/triple word with it, you're probably wasting it.
3. On your turn, look first for what double/triple letter/word squares are available to you. Then look at what words you can make to best utilize those squares. The goal is to score the most points, not make the longest words.
4. Don't allow your opponent to hit the triple world squares. Always assume they have it, especially when they only need an 's' to bridge a new word. If this means playing a word for a much smaller score, so be it.
5. Try to keep a decent balance of letters in your rack. Sometimes this means using up vowels or consonants at the expense of a few points on the current team.
6. Be careful of putting vowels next to double/triple squares, especially on the first word. 'RATED' may seem spiffy because you're using a double word, but when your opponent plays 'ZA' or 'OX' depending on placement, you'll already be down 44 or 36 to 12. Not good.