if you can understand the language you do a spell in would be best. while Latin would make a spell sound old and powerful, if you don't know what you're saying, how can you cast a spell properly? [same with people to tattoo Chinese symbols on their body when they don't know it. i speak Japanese, some of my friends and i were on the subway a few years ago and a woman came on with the symbol 'ka' tattooed on her neck, and we all laughed. she asked us what's so funny, and we said her tattoo and she asked us if we had a problem with 'wisdom' to which we explained the symbol was a question mark in Japanese.]
sorry of that tangent, i love that story. when it comes to cure spells, it depends on what it is. if it's a cold, a simple tea would work. if it's something like cancer, tea probably would not, you'd need a couple rather powerful spells at once. weather spells, while i haven't tried it, apparently do, but again, common sense is needed. if you live in Egypt, a spell for snow won't work very well. rain maybe, but this takes concentration and practice and above all, remember you're messing with natural forces so be careful what you wish for.