Starting from scratch

[nullshine]

As far as air compressors go, there are a few things to watch out for.

"Max HP" ratings. They don't mean anything useful as far as I can tell. I usually see 2 HP compressors with a big "5 HP MAX" sticker on them. Marketing crap, ignore it. Pay attention to the "Running" HP, and the CFM ratings instead.

Electrical service available in your shop. If you don't have 230V available in your shop, you won't be able to run anything above a 2HP (true 2HP, aka "running" HP). After that you will get into the 230V stuff. If you decide you want more compressor than anything in a 2HP, you'll need to get your garage wired for 230V if you don't have it.

As far as size goes, I probably wouldn't go with anything less than something with a 2 HP motor and a 25 gallon tank. Don't get sucked into any "big tank" models. The tank only holds the air, once that air is depleted, you have to wait for the pump to fill it up again! Somtimes having a big tank IS nice, as you can remove all your lug nuts without your compressor re-charging, but just remember that an excessively big tank doesn't really help you out that much. I have a 2HP with a 40 gallon tank. It's on the borderline of being excessively big compared to the motor/pump. Let me put it to you this way: I bought mine because it was a discontinued model and it was on for cheap. If I was paying full price I would have PROBABLY bought a 25 gallon. The big tank is nice, but check the price difference between that and a "regular" size tank. Also consider how roomy your shop is. Tank size is kind of a cost vs. space vs. benefit scenario. If you do choose to go to a 230V model, you'll probably end up looking at a 5HP, 60 gallon model. Should provide LOTS of air for a hobbyist, but to me it sounds like a 115V unit would be sufficient. Once again, evaluate cost vs. space vs. benefits. Whatever you buy, if you want to have it for a long time, buy one with an oil lubricated pump, the oilless ones tend to be... not so great.

Hose, fittings, tools, accessories, setup.
Plug your compressor directly into the wall. Use long hose instead of an extension cord.
Tools have a CFM rating that is usually based on a 20% duty cycle. Sometimes less. If a tool says 5 CFM on it, it will typically take 25 CFM to run it continuously. Just keep that in mind. Consider what tools/equipment you will be using. Probably one of the most taxing air "tools" out there is a sandblaster. They usually take lots of air(10-15 CFM for an average cabinet blaster), if you really want a sand blaster, check into which one you'll be getting and match your compressor to it (keeping in mind your desired duty cycle and budget), any other tools (ie. impact wrench, air ratchet, die grinder) will be taken care of due to their lesser air consumption.
Quick connect fittings. Choose a style and stick with it. If you plan on using high volume tools (ie. cut off tools) on the end of a long hose, pay attention to the ID of your quick connects, as they can restrict a bit. Other than that, a milton "A", "M" or "L" style will work just fine. I use milton "H" style, which quite frankly I probably don't need, but I hate restriction. I use 3/8" PVC hose with 1/4" NPT ends. The PVC is light and flexible, even in cold weather. Don't buy cheap PVC hose, it will harden up after a year or so, and be rock hard in the cold. Rubber hose is great, but heavy and usually expensive for good quality stuff, and oil/chemicals can damage it. Cheap rubber hose will harden up after about a year too.
Pressure side filter. Get one. Similar to these:
https://www.miltonindustries.com/uploads/Page_56.pdf
It will seperate out some of the water and oil, and they usually have a particulate filter inside too.
Horizontal vs. Vertical tanks. Horizontal takes up more floor space, but you could build a workbench/convenient shelving over top of it. Vertical takes up less floor space, but you can't build a work bench over top of it, but maybe a shelf depending on the height of the compressor. Your choice.

Here's some interesting info:
http://www.truetex.com/aircompressors.htm

Ok, after all that, here's what I would buy as a system for a weekend hobbyist:
-2 HP (115volt) with a 25 gallon tank. Oil lubricated pump. Choose horizontal or vertical tank depending on the shop setup you desire.
-x2 50 ft. long, 3/8" ID, 1/4" NPT ended good quality PVC hoses. One for clean work, one for dirty, rough work. You may end up replacing that one after a while. Quick connect them to make a 100 footer if needed. Go with less length, or maybe just one hose if you don't think you will ever need to have compressed air outside your garage.
-Female quick connect bodies. One at the compressor tank/output, and one for each of your hoses. As many male quick connect tips as you need (one for all your tools, and one for each hose and a couple spares for when you buy a new tool and invariably forget to get a quick connect tip). Choose the type based on your flow requirements. Probably just a Milton "A", "M", or "L" style.
-A pressure side filter like the above link shows.
-Maybe add a curly hose with quick connects if you want, it takes the weight of the hose off the end of the tool and makes working with the tool a little more precise.

That setup should get you going for all your common air tools like impact wrenches, ratchets, die grinders, air hammers etc. Really high volume stuff like a sandblaster would be extremely low duty cycle. Probably painfully low. Really painful.

One last reccomendation:
If you get an oil-lubed compressor, check out the oil drain on the pump and buy some brass fittings to relocate the drain in a convenient location. You will find you'll make your pump oil changes at proper intervals that way. The drain is usually in a really crappy spot, and makes the jobs a pain in the @$$.

Quick coupler flow/pressure drop ratings(mostly for interest, i'm sure an A/M/L will work fine):
https://www.miltonindustries.com/uploads/Page_36.pdf

Sorry for the rambling rant.