I hope your salary or promotion negotiation was successful. But sometimes it just isn't in the cards, or the raise you get isn't as much as you thought you deserved. Well, you can always look for another job, though you know what a challenge that is these days. If you really believe you are underpaid and you are unhappy with the place, you should look around. I'll give you advice on how to quit in the next section if that's what you want to do.
If you can't get the raise, maybe there are other things they can give you. In the section on negotiating your first salary, I mention a couple of alternatives. Maybe there are additional benefits or vacation time you could get, although these tend to be granted on formal schedules. Your company or boss may have more flexibility in giving you a bonus or stock grants and options. Companies prefer to give bonuses rather than raises because a bonus is a one-time increase which may or may not be repeated in the future. If your boss won't give you a raise, see if you can get a bonus instead.
Do you want to work from home, or have flexibility in the hours you spend at the office? Your boss could be willing to give you that if it doesn't affect the way in which you work with other people.
How about working on an interesting or highly visible project? In all companies, some work is more fun. Can you ask your boss to put you on a project that you'll find exciting - or one that gives you the opportunity to use or gain skills that might result in a raise in the future?
Lastly, see whether you advance your next salary review. Small or medium-sized companies will have more flexibility here, but if you can have a salary review in six months instead of a year, that's worth a lot.