The fishy smell can be caused by Gardnerella vaginallis. It won't actually hurt you as a male but can be passed to your next partner. You can't be sure if she is healthy clean unless you have her tested. However you can do what others are mentioning. The Whiff Test would be smelling before touching. Whafting is cupping your hand and fanning the scent toward yourself. Smelling, touching, and tasting are all truely called Organothalamic tests.
If you want to know its clean, only have sex with women you've known and have agreed to be tested WITH you. How do they know your penis isn't a disease-ridden syringe as it were? For intercourse use a condom until you are married and ready to have kids. For oral/penile, oral/anal, oral/vaginal interaction you can buy and use oral dams. Be safe and be smart.