Once you've decided accepting credit card payments online is for you, you'll need to evaluate your personal situation to see which credit card solution makes the best sense for your business.

And what factors determine which merchant service makes the best sense for you?...

1. Possibly the most important factor is the volume of business you expect to do online. Generally, doing a large volume of business online will warrant your own merchant account, a payment gateway and robust fraud protection.
   
   Why?
   
   Because you can off-set the inconvenience of a security deposit and the cost of a payment gateway by receiving a much discount rate. That means you pay less money per transaction performed.
   
   Again, this option only makes sense if your processing a fair number of sales per day.
2. Whether or not you already have a merchant account for processing credit cards off-line. If this is the case, and if you've established a decent relationship with your bank, enabling online payments is a fairly simple process.
3. Whether you are a shipping a "hard" good (something you can touch - eg. books, CDs, etc), or an intangible product (like software, ebooks, newsletter subscriptions). Some services deal with one type of good or the other, but not both.
4. Your profit margin. Free merchant services allow almost anyone to accept credit card payments almost instantaneously, but you'll be paying substantially more per transaction. If you're selling an ebook, where you don't incur shipping and re-stocking costs for every sale, it makes sense to pay more for the convenience of an "instant" transaction processing service.
5. Risk Factor: If this is your first online venture, you're probably not interested in forking out a $5,000 security deposit for the honor of accepting credit cards on your web site. The free services, where you pay ONLY when you make a sale probably makes the best sense for you!

OK... now that you've established where you want to be accepting credit card payments online...