[Darren]

I use 160 or 200# polyethylene pipe. For a long run like you're considering, you'll need to consider the effect of the internal friction of the pipe. The larger the pipe the less effect on the pressure at your hydrant. I'd vote for compression fitting too. They get expensive in the larger sizes but they're still cheaper than fixing leaks later.

After you dig the trench and before you lay the pipe, check the trench for rocks in the area of the pipe. As one of the posters mentioned, use sand in the bottom of the trench for pipe bedding. After putting about 4" of sand
in the bottom, lay the pipe and then fill around the pipe and over top of the pipe with sand to a point several inches above the pipe. Following that start filling the trench in layers.

You can either use an inverted spud bar to compact the fill or if you can use an air driven trench tamper which is designed like a jackhammer with a ram on the end. Either method will give you a workout, but you won't have settlement later.