1: Date and Payee
Start by writing in the date and payee.
Nothing too complicated yet. Just write the current date near the top-right corner. Most of the time you'll use today's date. You can also postdate the check. but that doesn't always work the way you think it will.
On the line that says "Pay to the order of", you'll write the payee's name. You may have to ask "Who do I make the check out to?" if you're not sure what to write in that line.
The person (or business) that you name on this line is the only one authorized to cash or deposit the check.
Unless they sign the check over to somebody else (and the bank allows them to do so), nobody else can legally do anything with it.
If you really want to control how the check is handled, you can prevent the payee from signing the check over or cashing it by writing "For deposit only to account of payee" -- that will require that the payee deposit the check in a bank account before doing anything else with the money (but this might make things too difficult for your payee).
Note that it's generally a bad idea to make a check payable to "cash". While this may be convenient for you, it's also convenient for anybody who wants to steal your money. If you're not sure who to make a check payable to, just hold onto it and don't sign it until you have the payee's name. Read more about Checks Payable to Cash .
Do You Even Need to Write Checks?