Props to examples of negotiating with a new offer!
Here are a couple ideas for raise at current place:
1) Study when he is not being approached by other people, approach him then. (Knock on door if closed. "Hi, it's Kevin. (Boss's name), I need to talk with you sometime. Is now a good time?")
2) Close the door so your salary conversation is private. If he's going to say yes, he won't want other employees to know.
3) Use the little speech you rehearsed, such as: "(Boss name), I work hard here and am proud that I've persevered here when others haven't. I've been comparing my salary to other places in the market and feel I'm worth more than what I'm making now. Based on my experience, someone with my certifications is worth $50,000 to 55,000. Can you arrange for me to be in that range starting next month?"
Key points:
a) When you start by saying you work hard, you are hitting a point he hopefully agrees with. If not, use a point he will respect. You just want to start by establishing a postive starting point he will agree with.
b) Once you start talking, he will wonder if you're going to quit. He will be relieved when you don't.
c) The second point ("I've persevered...") is to add another positive, build the suspense, strengthen your case and most of all give him a moment to sweat. It sounds a little threatening, though, so you could use a different point instead - "I have good quality reviews", any known aspect of good work that you have.
d) "Based on my experience, someone with my qualifications" gives him more reasons why you're worth a raise. Comparing to the market adds credence and gives impartial support to your proposition - makes it not personal. That's good.
e) Close by giving a range where the bottom is what you want, then ask for the order.
f) Asking for a timeframe gives a sense of urgency without requiring an immediate yes or no. He probably has to check and think; now you gave him a reasonable deadline.
If you don't like this script, write a different one. Practice it, then use it. Good luck.