Achilles tendonitis---what are tricks to dealing with it when active?

No tricks: Make sure you do your warm-up and cool down stretches consistently. Check your shoes and make sure they are not wore out. Adding an arch support or heel pad may be beneficial. Temporarily hold back on your exercise intensity or duration. If these things do not work, see a podiatrist.

Place a small : Heel lift in the shoe, this will preload your achilles' tendon so it won't have to work as hard. Ice it, physical therapy and stretching are good as well.