Starcraft 1 has a different psionic storm than Starcraft 2, so I'll only be answering Starcraft 2
It is 80 damage spread out over 4 seconds. Psionic storm is true damage and is not reduced by abilities or armor. Any unit caught under the storm (friendly or otherwise) will take 80 damage if it remains for the full duration. Its worth noting that Zerg units at full health will regenerate 1 HP when first hit. Storms do not stack. Any unit under a storm gains the storm effect. It is this effect which conveys the damage. You can only have 1 storm effect at a time on a given unit.
Depending on your army composition running through storms is often recommended you run from storms. Because there is a slight animation delay (1.5 seconds) you can negate a large portion of the damage if you act quickly.
Storms only hurt units. Units inside bunkers or carriers or other transport are unaffected.
Storms have a range of 8.25 to 9.75 as they have a radius of 1.5. Smart cast means the closest templar will energy will cast the storm.
The most important thing to realize is that 3 workers per mineral is the max you would want. It is not necessarily optimal however. The third worker is not as effective as the first 2. Once you have more than 2 workers, one of them will always be "hanging around" waiting for its turn to be useful. Therefore, if you have an expo with less than 2 workers per patch, you would do better to move some workers there. You will get more minerals per minute by having 2 workers per patch at your main and 1 per patch at your expo than you would with 3 workers per patch at your main.
With that in mind, here are some answers:
How to keep track of how many you have at a specific base?
Make sure all your mineral patches and gas geysers are visible on the screen. Now double click on one of your workers. This will select all your workers. At the bottom middle of your screen you'll see wireframes of all of them, 8 per row. if you have 3 rows full, that's 24 workers, which is a decently saturated base. "Full" saturation would be about 24 on minerals and 6 on gas, or 30. But if you have an expo, you're better off moving some of them... (Note that MULEs do not conflict with SCV's for mining time, so they should not factor into your counts.)
When you expand, should you build workers from that base or transfer?
This depends on the situation. If your expo is far away from your main, and there are potentially enemy forces in between, then transferring is probably a bad idea. If you have more than 2 workers per patch in your main, and your natural is nearby and well defended, then transferring makes sense. In my experience, Zerg players usually expand before they have much more than 2 workers per patch, while a 1 base terran or protoss will often build up 30 workers on one base before expanding.
**Rebuilding after some being killed **
I'm not sure what the question is here - you can just rebuild them like you normally build them.
Transferring when minerals run out
There is no automatic way to have workers move to an expansion when minerals or gas run out. However, you can listen for the voice that says "mineral patch depleted" and start transferring them. You can also look for the idle worker icon that pops up on the lower left hand side of your screen, that will alert you to a worker who is not doing anything.
Race Specific Tidbits
Protoss can chronoboost workers to help get an economy up and running, or recover from an attack.
Terrans can get by with less SCVs if they have a lot of orbital commands to summon MULEs with.
Terrans can load SCV's into command centers, then fly them to a new base.
Zerg players need to remember to build more drones to replace drones used to build buildings.
Best Answer
The original question was more about the difference between High Templars in StarCraft 1 (:Broodwar) and StarCraft II and if the "new" version is weaker. I really want to adress this rather than the current "How to use effectively". Also because I find the change pretty interesting.
Basic numbers
not compared:
Ok, so far this does not look like a real difference?
Abilities
In both games two High Templars can be morphed into an Archon without any special upgrades.
Dark Archons (morphed from 2 Dark Templars) used to have the Feedback spell in Starcraft 1.
In Brood War High Templars were useless (except for making archons) without any researches, but could learn 2 spells aswell:
Yeah... still looks pretty similar except I already have sentries for my hallucinations and can feedback w/o additional units and any upgrade cost. What you can tell me more??? Well then...
Psi Stooooooooorms!
Similarities in functionalitiy:
Gameplay
I haven't watched Brood War too much to know every little trick and usage of HTs in SC1 so maybe correct me or add sth. if you feel like.
Most of us should know the Mutalist Magic Box trick in SC2 (explanation video here), but something similar made caster control in Brood War so lovely. It means you could spread out your e.g. 4 templars, order them to cast Psi Storm once (1x hotkey + 1x click target position) and if done right they cast 4 storms that do not stack but are perfectly spread out and cover a pretty decent area.
an example screen from a TeamLiquid.net Guide: The key to spread spells
Demonstration video right here. As far as I know this is not possible with the smart casting mechanics in SC2, although you can hold down the hotkey for a spell and click at the desired position - which may be more accurate.
Besides this, storms are considered to be stronger in SC:Brood War because it did more pure damage and units had generally fewer hit points. For example it was able to chase away a whole terran army (consisting of vultures (80hp) and tanks (140hp)).
Some people may think the removal of Khaydarin Amulet weakened the HT even more (in comparison to SC:BW), because if it was researched you could storm right after the unit was warped in - now you have to wait ~25seconds to do that.
Summary
Yeah, maybe the SC2 storm does less damage and units nowadays have more hit points, BUT:
Keep in mind SC:BW and SC2 are two different games with quite different mechanics and therefore the unitroles have changed a little bit. All in all our lovely High Templars have their importance in both games. Get them, use them, win with them.
And don't forget some support units because they are squishy ;p
If I find some more nice screenshots and/or guides for storm usage in both games I'll add them soon.