ORIGINAL: whitecrest
In the summer, insect repellent is a must-have for me especially near sunset. Without it, it is almost impossible to fly as tiny no-see-ums will begin biting almost immediately after launching. I like the natural repellants using citronella and soybean oil that avoid using toxic chemicals.
I was flying at a 2 day contest a couple of weekends back and the bugs were so think that you really could not fly without insect repellent.
I took my first flight before I sprayed. What a mistake! The gnats were so thick that they were all over my sun glasses. ALWAYS keep insect spray or lotion in the car so you can't forget it!
A Tarp - I always put a tarp on the ground. (but Ed, you said this was about stuff for ourselves.) Have you ever dropped a tiny piece, a screw or a clip, and watch it go into the grass? Somehow you can see exactly what blade of grass it hit but you can't find it. So, for my funmble fingered benefit I have a 6X8 Tarp that I carry in the car that goes on the ground before I do anything else. It has saved many flying sessions. It also has come in handy when I have had to check something under the car or change a tire. And I have used it to cover my things when an sudden shower has come by.
A tarp is cheap insurance, to help prevent lost parts and a lost flying day.