Installing power from a metered pole to a shop 300 feet away. Looking at feeder wire available at Home Depot. Looking for 100 amp service. What size of wire in aluminum buried? There is also different abbreviations on different feeder wire? Any help appreciated. Also will it need a ground like 3-3-3-4? or just 3 feed wire not 4?

http://www.paigewire.com/pumpWireCalc.aspx?AspxAutoDetectCookieSupport=1



you only need 2 hot and one common, ground from breaker box to ground rod, not from the meter.

the calculator says aluminum 3/0 so a 3/3/3 should work.

My shop is wired like Hopalong says, this is "old code", but will work if there is not any metal lines, or other wire in the run path that would give a ground path back to the home. I'd use at least 2-8' ground rods set 10' apart at the shop connected with #8 copper wire and make sure the ground bridge in the shop sub box, is not connected from box to main common. New box should come with instructions on this part.

BTW, if you think there is ever a possibility you want to upgrade to 200a, best to add the appropriate wire and sub box with that in mind, will be cheaper now than later. 4/4/2 al should work for that at 300'.
If your near an electrical supply, you may be able to save some coin, I use Elliots Electrical supply in Weatherford and it saved me on wire vs HD and lowes by the foot. They have stores all over, so worth looking into.

Here is their web page, but there likely is a similar business closer to you worth a phone call.
https://www.elliottelectric.com/

Since it is service from the meter, current code is as Hops says, 2 hots and a neutral to the meter. You will need to put in a ground rod at the shop and do bond neutral and ground (use the screw in the breaker panel) since it is not a sub panel.

NEC (250.32(B)(1) Adds an egc, but also gives a couple exceptions, at least that is what I was told by electricians and the coop when getting my shop electrical priced. Could be situational depending on the property, like path back to main, water pipe, cctv cable ectra.

I did mine myself just as Hop said, with help from DT Cooper here on THF

That is true for sub-panels fed off the of the main panel. Service straight from the meter is different.

Mine comes str8 from my meter, or the mdc below it, below every meter is a main dc..right? As a safety requirement.

Yes, every meter has to have a disconnect/main breaker below it because past the meter it is always hot and can only have power cut by electric company.