I'm wary of any one-size-fits-all solutions. However, someone with intimate knowledge of how their web application works ought to consider doing some of these

I'm wary of any one-size-fits-all solutions. However, someone with intimate knowledge of how their web application works ought to consider doing some of these things on a case-by-case basis. I would avoid anything dealing the with User-Agent at all, because you never know if two years from now the most popular web browser will be called Mozilla WebHarvest or something weird like that.