When coding html/xul, use consistent "id"s.
If you are given a skeleton code having some of the functionality, from someone without a technical background, don't rely on that code. If it's not a lot of work, don't build upon that code. Don't even consider about the skeleton code. Just build from the bottom.
If you are given part of a user interface, and told that is how the client wants it, don't be constrained by that interface. Think from the bottom and decide on your own interface and tell that to the client.
Always ask the client what he needs at the END. Sometimes clients think part of the solution and tell that to you without telling what they need in the END. In the end, the solution that the client has thought is wrong.
When bidding for a job, and you can't decide on the amount and can only think of a range, place a bid near the upper margin and not the lower.
Have some logging mechanism from the beginning with a method to turn logging on/off easily.
Use version control.
Use CONSTANTS where applicable.
