Know the real price.
Always shop around other online stores to find the best purchase price for what you are looking for.
Know the return policy.
Return policies vary widely from store to store. Some online merchants do not allow any returns, and instead may give you store credit only. Some web stores have a fixed period of time for item returns. In most cases, you - the buyer - are responsible for paying the return shipping charges. Most Internet stores require returned items to be in re-saleable condition (original packaging, tags, etc.) and proof of purchase (sales receipts, invoices, etc.) so it is a good idea to keep the packaging boxes and other materials until you are absolutely sure you are not going to return your item.