Okay, first of all, how do you know you are getting the strafe jump right? Strafe jumps only increase your jump distance by a tiny bit, most "strafe jumps" are possible without the strafe. If you KNOW of a jump that IS possible with strafe jump, and not possible without, then... Here you go.
I'll try to describe it as best as I can. It is not a step by step sort of thing, so if you followed a step by step guide, you probably aren't getting it right. Just angle your view to the lower right by a tiny bit so you can still see when you need to jump, and run forward. When you press jump and immediately after that turn your view so you are facing forward.
Make sure you are using a class with lightweight and a submachine gun. Also, having your sensitivity on the highest setting will be most effective.