Here is a tip...Remember that only 1/3 of your depth of field is in front of your point of focus and 2/3's is behind that point. In macro photography, depth of field is your biggest challenge as it is very shallow since the distance from the lens to subject is usually very small. For that reason, pick your focal point as the place closest to the lens on the specimen. That way, you entire subject will be in focus. Also, using a tripod, get out of P mode(program), and got to A mode. Set your aperature as high as you can while maintaining a shutter speed that is reasonable to not have a blurred image due to camera shake or the subject moving.
Good luck, macro photography is a kick. I have loved macro photography as a scuba diver for sever years now.