[JeepHammer]

Common generators will come in three different drive types,

1. Combustion engine, Burning fuel in an engine to turn the generator.
(gasoline, diesel, LPG, CNG, Alcohol, ect.)

2. Wind Turbine. Wind power working to turn your generator.
There are several different kinds of theses.

3. Water Power. What we call 'Micro Hydro', or a very small water powered turbine turning your generator.

There are a few others, but they are as yet, fairly undeveloped...
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Then you must decide what you want your generator to produce,

AC, or Alternating Current, what the electric companies supply to your house right now, and depending on where you live the standard might be 96 Volts AC to 250 Volts AC.

Or,
DC or Direct Current, like your car battery stores and your car alternator produces.
These DC systems are usually in some standard configuration, 6 Volts, 12 Volts, 24 Volts, 36 Volts or 48 Volts.
Most are based on using 6 or 12 volt batteries to store the excess current for later use.
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So, once you decide what energy source you want to use to power your generator,
And what output form you want the generator to supply, we can narrow things down further for you...

Most people go with gasoline, diesel, LPG or CNG to power the generator,
And go with household current, 110 Volt AC output in the US since that is our standard, and they can run essential items directly off the generator.

 

[JeepHammer]

Getting ahead of things if the guy doesn't know what system he wants to use yet...

 

[JeepHammer]

What do the turbines have so that they won't get clogged up by water debris floating around?

It's called a 'Trap' or 'Grated Inlet'.
Where the water runs into your 'Collection Head' or 'PenStock', you simply install a slanted grate over the inlet, and that will angle most of the debris off the top of your collection box...
OR,
You build a small dam/retainer wall in the water stream, and collect your water from about 1' from the bottom of the standing pool.

This won't solve all your problems, you will eventually have to clean out your generator turbine at some point, but it will greatly reduce the amount of crap that can reach the generator.
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You will start out with a 'Collection Head' or 'PenStock', then the water will follow a pipe down hill.
The amount of drop from the collection head to your generator and amount of water (Size of pipe, Amount of water in it) will determine how much energy you can make.

A stream about the size of a healthy garden hose will turn a car alternator size generator, and those can be super cheap & simple to put together.
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NOW!
I'm not saying you can use a car alternator right off a car for this!
You CAN rewind a car alternator, add permanent magnets, and make a nice Micro-Hydro generator...
OR,
If you have a larger water supply, around a 3" line with good "Fall" so it builds up a lot of energy, you CAN turn a car alternator, although that isn't the most effective way to generate electricity.
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I've seen generators made from car alternators mounted in 5 gallon buckets make perfectly good current,
AND,
I've seen tethered floating docks with 55 gallon drums cut in halves making up a paddle wheel in the center of that dock turning generators that lit up community centers and pumped water from clean wells in the Jungles of Central and South America.

It just depends on what you have for parts and what you can do with them...
I have a friend with a VERY SMALL creek flowing through his place, He's got a 'Squirrel Cage' thing hooked up to a permanent magnet motor and it looks like crap, but works just fine!
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The 'PenStock' is the water collection and intake point, and you will need to use some sort of strainer there to keep the crap out.

The more water you can capture, and the farther it falls, the more energy it will deliver to your generator....

Interested in generator designs? If so, let me know and I'll try to find a few pictures and explanations.