Although not a comprehensive list hopefully a lot of common questions are answered below.
Q: where can I get some quick answers to a problem with my laser?
A: There are a number of laser furums around the web, you could do a google search or use the link below to a forum I highly recommmend.
When you post a question do not title it "Help" or "WTF", title it in a relevant way, something like "My 803T laser will not focus".
In the post put as much information as you can, it will help forum members help you.
Q: Can I connect my laser diode up to a battery to test it?
A: Of course you can...then you can buy a new laser diode to replace it. Laser diodes have been known to survive direct connection to batteries but rarely, is it worth the risk? More often than not it will turn your LD into an LED.
Build or buy a driver http://www.rog8811.com/laserdriver.htm
Q: My laser has suddenly stopped working, what is wrong with it?
A: Always assume it is flat batteries in the first instance, replace with fresh batteries. Make sure you put them back in the right way round. As a rule of thumb green lasers need the negative end of the battery toward the laser module (where the light comes out). Most other types and colours will have the positive end toward the module.
Q: I have measured the voltage of my batteries, they seem ok but laser still not working, any ideas?
A: Did you test the battery voltage under load, ie with the laser turned on? A green laser will draw between 200 and 300ma which will drag the battery voltage down if they are well used. Try fresh batteries.
Q: I have put new batteries in, they are the right way round, laser is still not working, why?
A: Check that all battery contacts are clean and shiney, also check that the threads that you unscrew to get the batteries in and out are clean and shiny as most lasers use the barrel/joining threads of the laser as part of the circuit.
Q: I have done all of the above why is my laser still not working?
A: I don't know but I do know some people who may be able to help.
Be sure to post all important information about what you have done so far.
Q: How can I turn my 5mw green laser into a 100mw burner?
A: You can't, in the early days of green lasers it was possible to get a much higher output by messing with the driver. Any mods made to current lasers will almost certainly result in the death of the pump diode.
Some owners of 5mw green lasers have been able to get a higher output by replacing the 2 X 1.5v batteries with a rechargable 3.7v battery and a spacer. I will admit to doing this myself and the laser is still working, I would not recommend doing this mod to a higher priced, higher powered laser as it may fry the crystals or the pump diode.
It boils down to "if you must have 100mw, buy a 100mw laser".
Q: what parts do I need to buy to build a burning laser?
A: This is a "how long is a piece of string" question, you have some questions to ask yourself first....
1) What colour do I want to build? (Red, Blu-ray or infrared)
2) Do I want to harvest my diode from a sled? (Red, Blu-ray or infrared)
3) Do I want to buy or build a driver? (Buy Rkcstr, Lava drive. Build LM317)
4) What host do I want to use? (Flashlight, labby, pointer)
With that decided you need some additional parts:
1) Safety glasses for the chosen wavelength (colour)
2) A module and lens for the laser diode
3) Heatsink for the module
Do your research (for a lot of the items you do not need to leave this site)
I can also recommend a few other places to look...
Tips for your first laser http://www.laserpointerforums.com/laser_pointer_forums_3/forum/showthread.php?t=40157
List of tutorials http://www.laserpointerforums.com/laser_pointer_forums_3/forum/showthread.php?t=36820
I will add to this FAQ over time.