well, i feel cautious offering advice to anyone with 5000+ posts (!), but i've learnt
- avoid names that 'could' have a site made for it, and stick to 'objective value', ie. high searched keywords, common company names or acronyms, or common phrases (that have more liquidity)
- beware of anyone offering to sell large amounts of people domaining information
- develop your names and hold for the long term (unless fads). developing helps you get into the mind of an end user. and the worst problem you'll have is sitting on a pile of money earners.
- offer real value to resellers (for me, website development customers) and you will never be short of business
- be courteous and helpful to anyone you deal with
- share your info with others
- be prepared to swap, haggle, deal, and work cooperatively
- plan your day before you start, so you don't trawl the web mindlessly
- find the best, few good tools to find names (pay for them if necessary)
- work towards names and sites you have an interest in (to get more than money for your efforts)
- follow warren buffet's rule: make a minuscule amount of buys. but when you see a bargain (whatever price bracket), buy hard. it's foolish to think that you can beat the market and spot deals all the time.
- there is a few more i put on namehugger.com
- good luck!