Toyota Repair: 1998 Toyota Corolla, toyota corolla, starter problems

Question
I'm currently overseas, the problem my wife is having with the car is that she can't get it started.  Sometimes it will turn over but other times it just makes a single click.  She has had the starter checked at autozone, and the battery is new.  Also, I had a friend put new sparkplugs in it. The only thing that I can think of is the ignition switch or maybe a relay of some sort.  I would appreciate any advice on this matter, so I can pass it on to her.

I don't know if this has anything to do with it, but my friend said that when he changed the plugs 1 and 4 were pretty filthy.

Thanks
Danny

Answer
Starter problems are very common on these Corollas, even though Autozone checked it there may still be a problem, it just happened to work while they were checking it and since I don't know what method they use to test the starter I can't take their word for it, I recommend that the starter be replaced since this is the most common failure on this model, I have never replaced an ignition switch or relay for this reason.  
The spark plugs have nothing to do with it.