Making a Launch Pad
This is the short tutorial but
 Commander Keen thought it was needed.
And since Commander keens site has helped me before with console commands I said I would do it..

So lets dive right in and start. 
Things needed for a pad to work.
1 A trigger push brush.
2 A target position
3 Link the two together with target and targetname.

First thing I do is build a brush the same size as the launch pad texture pick one out of the texture_ sfx  directory  Example sfx/launchpad_metalbridge04d .

Now apply this to the top of the brush all other sides use texture_common_caulk unless you plan on making the pad textured on the sides but this one has trim brush's for that.
Should look like this

Don't forget to rotate the texture if its needed just hit the S key then rotate until its pointing in the right direction.
Next I edit the edge of the brush to set the angle.
I try to keep it between say 36 degrees and 16 degrees, this is my personal feel because I think looks better if the angle is close to the arch of the players path.
To edge edit hit the E key hold the left mouse button on a control point and shape the brush. Until it looks something like this. You can also use the clipper tool to do this.




I don't put the trim brush's on yet because I might change the angle if I don't like it...
Next I build a brush the same size as the pad and put it right on top of the pad. I texture this brush on all sides with the common\trigger. Should look like this.

Next I right click on this brush in the 2d window and then select the trigger then trigger_push.
Here another pic to help.

Ok now that's done lets make a target_position 
First hit the ESC key to unselect the trigger_push. 
Then right click on the 2d window again then pick target then target_position.
Another pic to help


Now we need to link these two entities together.
First hit the ESC key then select the trigger_push then select the target_position and then hit ctrl-K.
This should draw a line between them and make it work.
Now move the target_position to the highest point of the arch of the players flying path thru the air.
This will take testing to get it just right so I have a little trick to help out. 
Build a small brush say 16by16by16, texture this with the common/nodrawnonsolid put this bush right in same space at the target_position. Once that's done with that new brush still selected hit the H key this hides it.
Now test the path by compiling map.
If the path seems off some select the target_position and move it. You can now hit (ctrl and H at the same time) and your little marker brush is showing again right were the target position was.
Now compile the map again and see if the path is right.
You can then use the nodraw marker brush as a reference as to were the target_position should go. Hopefully somewhere between were it was on the first and second compile. If not move the nodraw brush again and repeat....
When that's all done it should look something like this.

Now all I do is finish off the launch pad with some trim brush's and its done.

Its not a bad idea to save it as a prefab to use later.
You know how got to edit then save selected as prefab....
Don't forget to delete your little nodraw maker brush.

If you want to make a jump pad do all the steps above except start with a jump pad texture....