I began waitressing when I was 16 - in fact, it was my very first job. I went through months of training because the place where I worked wasn't just a "walk in and shadow for a week" type of job. This job required you to basically memorize everything before even having full confidence to take a table on your own.
I started off watching my trainer and then I was able to take drinks to tables. Once they saw I was comfortable walking and balancing a tray filled with drinks and food, they taught me the menu, starting with the easiest foods first. Once I got the hang of the menu, I was let go and took my first table, which was this sweet elderly couple. I was doing pretty good until I worked my first hardcore rush. This was maybe a month or two in of me taking my own tables, so I was confident, but not that confident. These two guys walk in and sat in my section, so I took their drinks and their orders, but like all servers at some point, I forgot to put one of the men's food in the computer, so he never got it, but every time I went to go check on their table, they said that they were fine, so I trusted it, not even thinking about the fact that I completely forgot to put his food in.
I decided to do a section run and check all of my tables, so I went to them and he basically embarrassed me in front of the entire restaurant. He called me out of my name and used other explicit words; I'm still oblivious at this point because they didn't tell me what was wrong, so I told him, plain and simple, "Sir, I don't read minds, so I can't help you if you don't tell me what's wrong." Then he stormed to the register, paid for his seven beers, and left, but not before telling my manager that I left his food out.
My manager was super sweet and calm about it and he came and told me what the deal was and told me to always double, triple check my orders before putting them in. I told him that I would from now on, and then I ran to the bathroom and called my mom because she needed to know that her 16-year old daughter was verbally attacked while working. Needless to say, she wanted me to quit on the spot and my brother wanted to come to the restaurant and give them a taste of their own medicine, but that wouldn't solve anything. Those guys never came back to the restaurant (or not when I was in there, at least).
Moral of the story: your server is not a mind reader.
If they forget to put your food in, tell them in a nice way, "Hey, I haven't gotten my food yet." and don't call them names. I wouldn't dare be rude to a person who is in charge of my food, even though it's a crime to tamper with someone's food in a public restaurant.
We're all human and we all make mistakes. It's just common courtesy to treat your server with respect.
If you choose not to leave a tip, then that's your business, but don't get an attitude with everyone in the restaurant when they ask you how was everything; just say good or it could've been better and go about your day. In the past, I haven't been the nicest customer (i.e when my 18th birthday was ruined), but I got over it because I know that these people are human, have feelings, and just want to go home at closing time.