Asking for a raise is difficult. In my last job we got annual raises. However, the gap between my salary and two other people who did similar work was tremendous. One of the others were a lawyer and teh other had a degree in engineering. I was looked upon as street talent by some board members. I offered suggestions and was sometime successful.
I was successful in getting raises for other people. So my best advice is to get someone one else to recommend you for a raise. It can be a co-worker or a supervisor. It just has to be someone who will say in front of the boss that "Bill is really an asset, He comes up with good ideas and puts in the extra time to make them work or something like that.
The only other alternative is to line up another job that pays more and then approach the boss with the fact that XYZ company has offered you a job payng ____________, but you would really like to say where you are. Can we come to some compromise so I will not have to leave here.
There is no easy way.