Originally Posted by trilerian

Clean the tabs of solder. You can use solder wick, a solder pump, or some braided wire with flux (essentially solder wick). The reason why the solder job doesn't look as good the next time is because all the flux was used up/burnt off. New solder with flux works wonders, but you have to get rid of the old solder or you just have a mess. For cleaning off flux you can use 99% IPA or brake cleaner.