The easiest way to lower rejects is to ping each one of the servers and choose 2 or 3 with the lowest ping... Add the lowest as primary and the other as failover-only.
Wait for an hour and then monitor your miner to see what's the percentage of rejected shares. Rotate the servers above if needed until you get it.
AND NEVER USE WIRELESS ... unless you can not mine otherwise
Really???
Good thing no one told me that when I first began mining. I've been using wireless for half of my mining power since I began, and other than the occasional dropped connection, I have had no problems whatsoever. In fact, my reject rate on that computer is lower even than that of my directly connected computer--which is quite low itself. That computer is in the opposite end of my house . . . about 70 feet or more away from the router.
As far as I can tell, there's absolutely no reason not to use wireless as long as you have a strong connection.