Quit relying on Tri-Met to get you home when you get a flat! It's easy to fix them yourself.

• toolkit
  • wrench to get your wheel off if you don't have a QR axle (quick release)
  • spare tube(s)
  • patch kit (replace glue yearly, it dries up)
  • pump that will mate with your valve style (Presta or Schraeder)
  • couple of bucks to use as a tire boot, JIC
• remove wheel
  • wheel anatomy!
    • axle
    • hub
    • spokes: keep wheel round, in one plane, and centered around the hub
    • rim: has a lip to hold the tire bead in place
• remove tire
  • start at valve side
• tube: replace or patch?
• inspect tire
  • don't use your unprotected fingers! You'll cut yourself on the glass/thorn/fishhook that may still be in your tire.
  • boot tire if it's torn
• inspect wheel
  • rim tape, spokes
• insert your new or patched tube
• reseat tire - don't get tube stuck between tire & bead. (Characteristic puncture: looks like a snakebite.)
• reinflate tube
• reinstall wheel

RIDE!!!

Pro tip: Practice at home periodically* if you don't get to do this in the field.

* requires beer