[ilaksh]

I think Freshbooks makes it easier to bill (it sends the invoice in an email), easier to pay (they can click on a link and use their credit card) and provides a 3rd party record. Also since its completely online, there is no excuse related to waiting for things to go back and forth in the mail.

Usually if they don't pay right away I explain to them that I need them to always pay within a day or two. If they forget to pay after that, one extra email or IM is usually enough.

You might have to actually call them.

I also tend to not work on a project between the time that an invoice goes out and when it is paid.

From my experience once they are actually aware of the bill they usually pay within 0-3 days. If it takes longer than that, maybe you can get better clients.