It depends what you want to do, however I will assume it is just you want something basic to start from rather than because the police (who also happen to be signals intelligence for your country and are willing to use the crazy restore techniques) are about to kick down your door and you need to get rid of the evidence on one and burning the thing is not an option. If you just want to hand it to someone like me that knows about recuva and
http://www.cgsecurity.org/wiki/PhotoRec then a full format (rather than a quick format) will do 99% of it, if you want you can use a file shredder that overwrites things and makes that even harder but a full format will do. Even deleting everything and then making a file to fill up the remaining space will do, though I might be able to recover some file names in some cases.
Yeah I would not fully format a flash drive every week if I really wanted it to stand a chance of outliving me but if you want to do it just to start from scratch then you are far more likely to lose it, stand on it or otherwise have it be unavailable before you run out of sector lifetime. It is defragmenting that is the bigger worry for people. People have tested SD card endurance (which is basically the same tech as USB flash -- it is all NAND chips) though
http://forum.embeddedarm.com/showthread.php?3-SD-card-endurance-test
For most purposes plain old windows format will do the job. Maybe bump it up to the diskmgmt.msc program if you want to get really fancy or use some options plain old format decided was not useful to the average user (some of the sector sizes and file system types, especially on larger devices). The panasonic SD formatter (not sure what it is called these days but that search should find it) is a great tool though.
If you have Linux (or one of the other X86 compatible non windows, non mac operating systems) then gparted is a wonderful tool. It is far more powerful than just a basic format tool though and is aimed more at sorting partitions of drives. It might not be installed with the basic OS but it should be in the repos and if you have any kind of rescue disc it will almost certainly be on that, or if you want it standalone then you can do that as well
http://gparted.org/download.php . Indeed short of needing the forensic stuff or crazy recovery tools it is probably the best I know of, I certainly would not pay for something unless I needed it for a crazy file system for my server (and in most cases there I would wait a few months and gparted would probably get it or it would come with my server install media).