Generally speaking, you shouldn’t expect more than one raise during a 12-month period. If your last raise happened within that period, maybe hold off for a little bit.
Remember when you first applied for your job and reading through the list of responsibilities? Maybe that list has expanded since you started your position. Show tangible examples of how much your value has increased and how your performance has been a benefit to your company.
Do some research and find out what similar positions in your area are making. Any raise should be in relation to these salaries. The more information and evidence you have to back-up your request, the stronger it will be.
If your company is going through financial troubles or you know it’s been a down year, it may not be the best time to ask. Part of being a good employee is being a team player. So if that means you need to wait until the company is back on their feet, and you do not want to find a new job, that’s what you’ll have to do.