CLOTHES: Avoid wearing boots. I know it's hard for some of you but there are nice other open shoes you can use. Not wearing boots won't make you less goth than you are and it's way better for yur blood circulation an..well..feet odour! xD I suggest you use flip flops or platform sandals or flats (see pics!). Maybe add some fake tattoos on your feet or ankle skin to make it more eye-catching. Try to avoid thick socks and leggings. Wear light clothes. Try avoiding black (it attracts the sun and can get you sunburnt more easily)..go for white clothes to spice up with some thin accessories.
HAIR: Keep 'em hydrated! Use an oil based hair mask at least once a week! Try to keep your hair up in a ponytail and pin up your fringe. You'll sweat way less this way. Use a hat or a bandana or parasol to keep them away from the sun.
SKIN: As we all know, the main problem for goths is the tanning. I personally don't mind getting tanned (beside the fact that I already am naturally tanned, I enjoy getting this exotic look that makes me look like Cleopatra xD). But for all of you with white skin, if you don't want to get sun burnt or get those ridicolous red ,orange tan, please follow my instructions: As I said in the post on how to get a perfect skin, there are some hydrating skin lotions with sun protect factor. Put it on especially in the morning and wait until your skin absorbs it. Before exposing yourself to the sun, wear a sunscreen lotion with the highest SPF ! (like the one for kids xD) and wait until it is absorbed by the skin (takes usually 20 or 30 minutes) otherwise if you don't wait the lotion won't work and it will "fry" under the sun. If you can, stay in shade or hide under a parasol. After the sun exposure, go home and wash yourself with soap (using water only will make the tan stay). To be sure not to have got sunburnt put an aftersun lotion.
If you have other ideas or things to add, please tell in the comments! ^__^