neem oil you should really hold off for the last 3 weeks of flowering and use it sparingly when you do use it. Or don't use it at all.
for spidermites (which are a fucking bitch) make sure you cool that environment down as much as possible. Like 60 degrees if you can at night. That slows the mites way down.
I use yellow sticky traps that you can find here:
http://www.alternativeco2.com/Grow-Accessories-s/43.htm
then nail them with some of this spicy, minty stuff that's at home depot and switch that off with some nasty smelling stuff from the grow store.
I can't remember what either is called right now. But a lot of things work. The point is to use several methods so they don't get used to one. Hit them in waves so that you kill the eggs, newly hatched, and any random survivors from each wave.
You have to be thorough. You won't get them all the first time. Don't give up just because some are still around. You have to be persistent.
You'll never get rid of them all for the rest of the grow but you can still salvage it.
Constantly keep an eye on them if you have spidermite problem. If you see one plant heavily infested try to use a little vacuum to suck them off.
If you ever see a shitload of them on some plants move those plants into the shower and just hose those fuckers down so you wash all the mites off of the infected plants. Unless they're not worth saving. But if they already have decent buds and are healthy for the most part you probably want to try and save them.
Constantly clip dead leaves so that you don't give them stuff to feed on or places to hide. Clip the bottom leaves even if they're healthy. These are mite breeding grounds. There should be no bushy little leaves at the bottom of each plant. It won't get you shit for bud and will just provide a breeding environment for mites and other bugs. As well as will take energy away from the plant producing growth where it matters.
Light doesn't hit the bottom of the plant well enough anyway so make sure to trim the bottom of those plants well.
Be looking for speckled leaves as these are places where they are getting crazy even if you think everything is going fine.
Worst comes to worst bomb that room as long as it is less then 6 weeks of flowering.
I hate spider mites. Good luck. But neem oil tastes nasty. I've always used different methods.
People say ladybugs work but I've bought tens of thousands of ladybugs and had them flying around my place all over and I still had bad problems. In my opinion ladybugs don't work much at all and get to be a pain because now you have more bugs flying all over your house. Then they fly up to the lights and die and you have all these dead ladybugs to deal with.