How can you saturate mineral fields effectively?

I know that you should have 3 workers on each mineral to harvest it most effectively, but how can you manage how many workers you have to use per base?

The number should obviously be 3 x mineral patch, but how can you easily keep track of that quantity? How can you re-build them (reaching again optimum quantity) after some of them being killed? If some patches are depleted, how can you easily transfer some of them to an expansion (leaving some to finish off the ones that are not depleted)? When you expand, should you build workers from that base once it finishes building or transfer some from the main base?

I think that with those questions I'm asking for a drone/SCV/probe guide.

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.

Peter covered much of what I would have said, but let me toss out a few more tidbits:

How to keep track of how many you have?

You can double-click a worker, but you can also control-click, or draw a box around the mineral line if there are no other troops nearby. I prefer control-click since I sometimes miss when I try to double-click.

When you expand, should you build workers from that base or transfer?

As Peter said, generally you only transfer if you have more than 2 workers per mineral patch and if it is safe to transfer them, and a short distance. But one reason to transfer them regardless is that afterwards, both your main and your expansion can produce workers, effectively getting back towards saturation at twice the speed.

A nice option here for Terrans is to build their second command center in their main base, load it up with 5 SCV's, and fly to the expansion spot. Works especially well for island expansions!

A Zerg Specific Tidbit

Remember that Zerg can send drones through Nydus worms. Nydus worms allow instant travel and can be built without creep, so I like to pop one up where I'm expanding, to allow drone transfer and immediate reinforcement if necessary.

Well, like the great old Starcraft 2 tip bars said, the key for a good economy is to be constantly building Drones, Probes or SCVs. Even if you surpass the 30 you need to saturate your first base, you'll split them when you expand, so always keep on building them! I usually stop when I hit something around 70 in a classic team match. 1v1 is kind of different since you have to "calculate" how much the extra worker will cost(not just in monetary value but also in overall value towards gaining an advantage over your opponent), so keep on scouting to know if you should push economy or army!

As an extra suggestion, when you get an expansion, the goal is to double the minerals your earn and to double your production. To do that, you need to let your main base work as long as possible! I would say that you should split your workers between bases EVEN if you dont have 2 workers per patch in your main.