I'm often asked for tricks to help get motivated to workout. I wish there was a magic answer, but unfortunately, I haven't found the perfect motivator that works for everyone. However, I have had luck with these tactics:

Tell a co-worker, partner or friend that you are going to workout the next morning, afternoon or evening. Knowing that someone will follow-up with you is a good motivator.
Find a workout partner and set up a time/day to meet up at the gym or park. Don't make it a long session - start with 20 or 30 minutes. Also, make sure it is someone who will show up and hold you accountable to working out.
Pack your workout bag or set out your clothes the night before. I had one client that went to extremes - she would sleep in her workout clothes!
Schedule your workout time into your calendar. When I worked in a corporate environment, if I didn't block off time for the gym in my calendar, it would get filled up with meetings or other activities.
Tell yourself that you will try it for 10 minutes. After 10 minutes, if you are completely miserable and hating it, then you can stop. I use this tactic more often than I would like to admit. Most of the time, I'm well into my workout once that 10-minute mark hits; however, I have stopped before. And, that's ok.