If you have been creating Motion or Shape Tweens you will notice that they make a straight line from the first Keyframe to the next. In order to give the path it takes some shape we must add a guide layer. A guide layer acts a track that our object will follow along.
The two animations below show the difference between a simple motion Tween and a motion Tween with a motion guide.
Now that you have seen the difference between a Tween with and without a guide lets try to add a guide layer to a Motion Tween.
Step one: Be sure that you have already created a motion Tween between two Keyframes and that your object is not stationary throughout the duration of the Tween. Your time line should look something like this:
Step two: We must now create a guide layer for our motion Tween. Left click on the first Keyframe of your motion Tween. Next, click on the motion guide button in the timeline, or go to Insert > Timeline > Motion Guide from your pull down menu. You should now have a timeline that looks like this:
Step three: Now we must draw our guide. To do this select the pencil tool from the toolbox. If you want to change the pencil options you can do so now.
Once you have your pencil selected you left click in the very center of you object and draw your guide to an approximate location of where your last Keyframe is.
Your timeline should now look like this:
Go ahead and test your movie your object will now follow the guide.
Step four:We can now choose if we want to Orient to Path. What this will do is instead of the object always facing the same direction throughout the duration of the path we can choose to have the object orient itself with the path. What this will do is make the guide layer similar to a rollercoaster. When your line angles up, your object will face up. To turn orienting on or off left click the motion Tween to get the Tween options in the properties pallet. At the bottom of the pallet there is a box you can check which says Orient to path.