PayPal is the most convenient for most clients, since it is reputable and used ubiquitously. The downside is that if the invoice is large > than $3000, you will lose a good chunk in PayPal fees.
Checks are great because you get to keep all the money...well, except for taxes later,
Wire Transfer (Bank) is a great option if the invoice is huge (more than $3000), to avoid costly fees.
The other options suggested above are good alternatives, too.
Comments
PayPal is the most convenient for most clients, since it is reputable and used ubiquitously. The downside is that if the invoice is large > than $3000, you will lose a good chunk in PayPal fees.
Checks are great because you get to keep all the money...well, except for taxes later,
Wire Transfer (Bank) is a great option if the invoice is huge (more than $3000), to avoid costly fees.
The other options suggested above are good alternatives, too.