Sourdough Starter isnt rising I've been working on a sourdough starter for almost 3 weeks and I can't seem to get any rise out of it.  I feel like I've tried every trick I've read online and nothing has worked.  

I started with wheat flour and then switched to white after the first feeding.  After a few days of measuring with cups I've since been measuring by weight.  I had some hooch early on (maybe day 3-5?) but only small amount, if any, since.  I get a varying level of bubbles but no rise.  I've done the float test and failed.  I've tried everything...feeding every 12 hours, feeding every 24 hours, doing one feeding with wheat flour, feeding 1:2:2, feeding 1:1:1, you name it.  I've tried keeping it in a pyrex bowl with a towel on it, pyrex bowl with lid, in a mason jar with saran wrap, mason jar with lid tight, etc.  I tried each of these for a few days before modifying.

The only thing that seems to have gotten any rise was when I put it in the microwave with a cup of hot water - I've done this twice and the 1st time I got some decent rise out of it, the 2nd time nothing really.  I live in Florida and its very hot/humid so temp shouldn't be the issue.  

Consistency is normally very thick after I feed but when it comes time to the next feeding its very runny and thin.  

Does anyone have any tips on what else I should do?  Am I just trying too many things?  HELP!
How exactly are you feeding the starter? Are you just adding new flour and water or are you discarding?

What I do (based on recipes I've seen) is discard 2/3 of the starter and add 1/3 of each new flour and water. So if I have 100g of starter, when I feed it, I discard 67g of it and add 33g of each flour and water.

The reason for this is that it gives the starter a lot more "food". If you start with 50g and add 50g, you've added 100% and then have 100g. If you then add 50g more, you're only adding 50% and have 150g. If you add 50g again, you've only added 33% and have 200g. Because you're adding progressively smaller amounts of food, you will get progressively less activity.

Instead if you discard 1/3 and add 2/3, you'll add 200%, and if you do it again, you'll add another 200%, etc. After a few days of this you should have a very active starter.

This does require discarding some of the starter which is why I keep it relatively small. I use 75g of starter for a loaf of bread, so with 100g I have enough for loaf and then enough to re-make the starter.

The discard can be used in other recipes such as pancakes, banana bread, etc. It is 50/50 flour and water so easy to substitute into other recipes.

Aside from that, you will get more activity at a warmer temperature.  Room temp is usually about 65-70F but the yeast is more active at 85-90F.  But don't go much higher than this or you can make the yeast so active it will produce alcohol or kill it completely.  You can get to this temp a bunch of different ways.  The space above or behind your fridge is often warmer.  If you have an oven with a light, the closed oven with the light on is often warmer.  If you have an aquarium heater those usually hold this temp.  Many electronic devices like computers or wireless access points generate a little bit of heat.

You should not microwave the starter, this will warm it up but you'll probably kill the yeast.  When you are about to feed it you can microwave the water you're using to warm it up first, but don't microwave the starter or flour.

If your water has a lot of chlorine in it, that can inhibit yeast growth. You can either use bottled or filtered water, or leave some water sitting out for a few days to let the chlorine dissipate.