One tip I might suggest is to keep a loose-leaf binder of useful material. If you can't afford to buy, say, that wonderful book on jewellery you ve got out from the library, xerox the parts most pertinent to you, note the source on the first page, and put them in the binder. This will help you to build a pictoral library and will allow you to make critical comparisons simply by flipping through the binder. Comparison also means talking with your fellow researchers, be they beginners or seasoned explorers. This is the perfect time to float theories you're developing, to share the results of practical experience, and to trade information.
Every researcher is different.
Others still will have seen books you haven't , or will bring a different perspective into the picture. Take, for instance, the study of medieval coins. The economic historian will discuss them in the context of the exchange of goods and price theory. The gold or silversmith will be interested in the way they were minted. The art historian will be interested in what s pictured on them.