Make sure your assembly area is spotless.
Wash your components with mild soap and warm water after they come back from the machine shop. Even if the shop did a second cleaning, there will still be pieces of ground iron stuck in block passages and crank oil holes. Blow dry with clean(filtered) air, and wrap componenets in engine bags(heavy duty contractors bags work well) to prevent moist air from causing rust to start on your fresh parts.
Measure everything twice, write it all down in a small note book, not scraps of paper that can get lost just when you need them.
Degree your camshaft, it is a neccesary part of building a high perfromance engine. Theres a reason every professional builder performs this task on every motor they assemble.
Do research on the parts you intend to buy, whether they be new or used. Saving $20 on a Chinese part may bite you in the ***. Buying used parts unseen can be risky, so ask the seller for lots of pictures and as much info as possible.
Theres a lot more, but this will give you a start