Provide some type of incentive for them to contribute. Have a contest with a prize. You should have included a link to your new website here. Recruit in the tennis warehouse forums. Good luck!
Make sure you have plenty of water/ sports drink. If you feel thirsty, chances are, that you are already a bit dehydrated. Start drinking 2 hours before you even get on the courts. Dri-fit boxers/briefs by Under Armour are much more comfortable in hot weather compared to cotton underwear...