BGP Path Filtering

I'm having a hard time finding best practices for filtering outbound bgp announcements when providing transit to bgp-speaking customers. While we currently multi-home to several providers it appears we will soon need to provide transit for customers with their own AS's. I find lots of references (and understand) the basic ip as-path access-list 3 permit ^$ and it would seem that should we wish to provide transit for a bgp customer AS12345 we would use: ip as-path access-list 3 permit ^12345$ but I think this breaks if AS12345 prepends their advertisement. Next up is: ip as-path access-list 3 permit ^12345_[0-9]$* Which seems correct to me. Is this still best practice (or even correct)? Mark Radabaugh Amplex (419) 720-3635