I am building a detached garage 300' feet from my home and main breaker panels. The meter is out by the road right of way 450' from the home. The garage is going to sit somewhere in the middle about 150' down the hill. Rather than tap into the house panel I'd like to come right off the meter at the top of the hill. The local power company will not allow a DIYer to touch there meter or feed so I know I'll need a licensed, bonded electrician. My question is, is this a sound plan and will most power companies allow a second tap off a meter. Also, at present I only need three 15 amp circuits in the garage panel but for future expansion want 240v. How large of a wire should we use coming from the meter to the garage? Any other suggestions? The soil is mostly rock and I will have a heck of a time driving a 10' ground rod.

There is about 0% chance you can come off your existing meter with a parallel service cable.

You would need to either replace the meter with something that allows parallel load side (IF the POCO will also allow it), or install a feed-through panel at the meter and the house from the feed-through lugs and feed the barn off a branch breaker.

It took a few days for the local power co-op to get back to me but they finally called today. I must be having a lucky week because they do allow a second tap off the meter. Kind of surprised me but they said after the meter lugs everything is mine and I can do pretty much what I want except tie to another property or business. Its hard to get a licensed electrician out to do or look at a job in this rural area but I have called some. I just want to better prepare myself with what is needed rather than allowing the electrican to tell me. Maybe that's not so bad but my question is what size wire and panel would be best to run. For now this will just be a garage with 120 circuits for lights and about 10 15 amp outlets. I do want the option to add a 240 welder or saw down the road. Any suggests would be appreciated.

A second tap off the meter is different from "after the meter lugs".
What I mean is typically the meter pan lugs themselves are not likely capable of supplying two sets of service conductors. Meaning you can't simply stick a second wire under the lugs.

120 and 240v are all well and good. Pretty much ANY feeder to a detached structure will be 120/240v anyway.
What will you run?? From your description a 30 to 60 amp feeder will be fine.
Depends on the welder, the saw and any other potential equipment you might run.

If it were me I'd go with a 100A feeder and #2AL conductors. 150' is no that bad as far as distance goes.
If you get a stick welder and a compressor a 50 or 60A feeder might be too small.

The 240v isn't currently a need so Its hard tp predict what I, or future owner, might eventually add to the list of tools. Some table and arm saws I own can run 120 or 240 but currently are set for 120. The light wieght welding I currently do is 120v wire feed gun. Thanks for the advice so far. Now if I can jusrt get an electrical contractor to show up out there all will be fine. Bob

Don't even question the "need" for 240v. As I said, for a feeder such as this it will be 120/240v anyway.
It makes absolutely no sense to run a 120v feeder. There is NO $$ savings and you will only serve to limit yourself later on.