Waiters and waitresses rely heavily on tips to supplement their wages; it's just a fact of life. Unfortunately, that's the way the industry is, and we all know it needs to change. But until that happens, if you can afford to eat at a restaurant , you can probably afford to leave a tip for your wait staff, especially if they've done a good job. But some people take it upon themselves to determine whether or not their server needs a tip without really knowing their circumstances. You can learn a…