How to incorporate a half marathon into marathon training?

Base your goal on your current training. If you are hitting your paces in training for a 2:55 marathon then base your half marathon pace off that. If the calculator says 6:20 pace run that for the half (or try to). You don't need a real taper, just don't do any hard workouts and drop your mileage a little bit for two to three days before the race (a sort of mini taper). The half should give you an idea if your marathon goal is realistic and ideally the courses will have a similar elevation profiles. If they are radically different, you can calculate adjustments. As long are you runing within a minute of your goal in the half, you should be okay. If you are slower than that you may want to rethink the marathon pace unless some outside factor slowed you down. Good luck.

I think you should be 6:10-15 pace for the half to be solidly in shap for a 2:55 marathon. As noted above, do a mini taper before the half. After, just run a lot of easy miles and do one last solid long run. Racing a half marathon will not mess up your full. Go out and enjoy the race. Run hard--don't make it some fussy time trial workout. You are a runner. Race. Have fun. Don't over analyze.

Thanks replies. I am glad to hear that I do not need to plan much of a taper. I am going to target 1:22 and hope for the best. If am much slower I will have to think about adjusting my marathon goal.