Tips Before You Start
Here are a few things to make your experience with drippers easier!
Different Types of Drippers
There are two basic different *types* of drippers and many different *styles* of drippers.

Installing in 1/2" polytube
As we mentioned above, you should use a punch made specifically for this purpose. The proper punch will make the correct size hole so the stem on the barbed end of the dripper will fit tight and seal correctly. For this reason, please DO NOT use a nail, or other device, to make the holes in your tube. The punch is where it's at!
Every dripper has a water inlet and a water outlet. The water inlet has a small stem coming from the dripper which ends with a barb. This barb helps to hold the dripper in the tubing while the stem is what the tubing wall seals against. This is why the hole needs to be an exact size. (Don't forget that punch!)
The water outlet can be a hole flush with the body of the dripper or a small stem protruding out from the dripper body. On some models the outlet may even be barbed.
To actually install the dripper, use a punch and make a hole in the 1/2" polytube. When using a hand punch, hold the tubing in one hand to place pressure on the opposite side from the hole. Push the tip of the punch against the tubing and twist it back and forth while pushing. This helps the tip of the punch to cut through the tubing and not just rip through it. Like we mentioned in the tips section, the better punches will actually cut out a hole in the tube.
Now take the dripper and push the barbed end into the hole made by the punch while still supporting the opposite side of the tubing with your hand. Push the dripper in until you hear a "Pop" or "Snap" sound. This will mean the barbed end has gone past the tubing wall. If the tubing is very warm you may not hear anything but just "feel" the barb push past the tubing wall. After a few times, you will get the hang of it.
Installing in 1/4" Polytube
To install in 1/4" microtube you just push the barbed end into the end of the microtube. If you have a hard time with this you may always dip the barbed end of the dripper in some liquid dish soap. This will help it slide in easier. Even better than the soap is to fill a cup with hot tap water and let the microtube ends soak until they get soft. Then insert the barbed end and let the tube cool before moving it around much. We have found this to be the best way because when the tubing cools it shrinks around the barb very tightly.
If you have to take a dripper out of microtube *never* cut the tubing off! If you nick the barb on the dripper it will leak when re installed. Work the dripper off the microtube by pulling and moving it back and forth. You can also pry the microtube back using your fingernail. Once the dripper is off the tubing, you will need to cut the tubing back about 1/2" so the end which had been over the barb is gone. The barb deforms the tube end and if you just install a dripper in this end again it will not hold well......trust us we have done both!
Replacing Drippers
Like we mentioned above about the ends of 1/4" microtube, when a dripper is removed the barb will have deformed the microtube and you should cut off about 1/2" before placing another dripper or the same one back in.
For 1/2" polytube you can just pull out the dripper. Try to pull it straight out, otherwise it may "rip" or "tear" the tubing around the hole. You can just pop another dripper in the same hole but make sure to test the seal by looking for leaks after the water has been turned on. If there is leaking, it is best to take out the dripper and install a goofplug to seal the old hole. Then make a new hole within a couple of inches and install the dripper.
When using a goof plug to seal a hole, note there are two ends on the goof plug. The smaller end is the correct size to try first, but if the hole has been ripped or enlarged this end may leak. In this case take it out and use the large end. When doing this the best way is to get a pair of pliers and grip the goof plug by the small end. Then while supporting the back side of the tubing, push the large end straight into the hole. In our experience this will seal all except the most badly damaged holes. If this is the case your only alternative is to cut the tubing on each side of the hole, then install a coupling.
Multi-Outlet Drippers
Most multi-outlet drippers are made as conversions from conventional irrigation systems. The models we carry all connect to 1/2" male pipe thread, which is your common sprinkler riser type. In simple terms, they screw right onto an existing sprinkler riser taking the place of the sprinkler. Because they are replacing the sprinkler they need to take the place of watering many plants in the area covered by the old sprinkler. This is why they have multiple outlets.
Another difference of these multi-outlet drippers is that you connect 1/4" tubing to the dripper and run it to each plant without placing anything except a stake on the end of the microtube. Depending on the amount of outlets and the flow rates you can water just a few plants or many. You will need to install a model which has the right amount of outlets for each area.
To install one of these multi-outlet drippers, first remove the old sprinkler. Then turn on your water to flush out any sediment in the lines. Next clean the threads on the riser. Then place a few wraps of Teflon tape on the threads and screw the dripper on the riser. Run microtubes from the outlets on the head to your plants and use a microtube holding stake on the end of the microtube at the plant. Turn on your water and check for leaks at the base of the head on the riser and the flow from each of the microtube ends.
Note the directions about the model you have because some can be adjusted, some can have outlets turned off and others may need to have the barbed connecters purchased separately.
Troubleshooting
Most of the troubleshooting tips have been mentioned above but here are a few more.