Create a contact in the Contacts app with just the information you want to see entered in online forms. In Settings > Safari turn on Use Contact Info, then select the contact using the My Info item just below.
Anyway, that's how it is supposed to work. I don't use it myself.
If you are wanting credit card and/or password's saved/autofilled, the options below need to be turned on. In both cases you will need to visit a site, or be asked for your credit card, and enter the data at least once. You will be asked if you want to save your password (or credit card) info. You can say yes, later, or never. If you say yes the next time you visit that site, or are prompted for your credit card, the information will be entered automatically.
The Saved Password and Saved Credit Cards options will let you browse already saved items, and delete them if you decide you don't want them saved anymore.
Because sites use a wide variety of protocols and tools not every site will work with these options; though most should.
P.S. I don't recommend enabling the credit card or password options if you share your iPad or leave it laying around without the passcode lock enabled.