It's All About Stability

• You need to immobilize your bike to safely tie it down. This means wheels won't turn, and the bike doesn't sway back and forth. The easiest way to ensure stability and immobility is to stand the bike straight up rather than leave it resting on the kickstand. If you have a center stand, you can use it, but the using the wheels actually gives you a more stable base.
  
  Distribute your tie downs evenly and tie them as widely as possible. If the bike is in the back of a pickup truck, place it in the middle and tie the straps (or ropes) to the front and rear corners of the bed. This will allow the ropes to hold the load more firmly than if they were tied closer toward the center.
  
  

Choosing Tie Down Points

• Anchor points are easy to pick--a trailer or truck bed usually has good anchor points in plain sight as part of the design. Tie down points on the bike are a bit different and take a little more thought. The idea is that you will be grabbing a firmly mounted part and using it to compress the suspension slightly, so whatever part you use, it has to be structurally sound.
  
  Most people use the inside of the handlebars, as close to the upper triple tree as possible. Depending on if you have risers or not, you may even be able to tie the bike down using the upper triple tree itself. If you don't know what the triple tree is, you can find it holding each of the fork tubes and the steering stem, right at the front of the frame, and the top of the forks. Tie down points in the rear are tougher to find, but most people prefer to find an exposed part of the frame or suspension.
  
  

Tight, But Not Too Tight

• Once you've picked the tie down points and anchor points, it's time to tighten everything down. Tighten the straps or ropes evenly from side to side to prevent the bike from tipping to either side. As you tighten the straps, you'll notice the suspension compressing. This will help to keep tension on the straps or ropes and hold your bike firmly while in transport.
  
  Tighten everything down, but be careful not to tighten too much, as too much sustained compression in the suspension can damage the fork seals. Test your tie downs after you're done: the bike shouldn't move side to side more than a few inches, if at all, and should not roll back and forth at all. This means leaving the bike in gear.