We generally don't have aid stations or mile markers in races. I just learned to run by effort when I was a total newbie, and I carry food, fluid, gear in a pack. Mileage markers can be confusing if you don't know where they were measured from. I do use landmarks are guides for approximate distances. I usually map the stuff out ahead of time so I have an idea when I should be hitting those landmarks, if the map was right. (I do have gps stashed in my pack - out of sight - that I can map my run later and check the mileage.)

If you get a decent pack or belt that works for you (becomes one with you), you may not notice it. Carrying that much water for multi-hour long runs can get cumbersome, as I discovered. In the future, I may plan to loop back by my car in, say, 3 hrs (I'm slow, but training for longer run), and refill.

Others may plan routes by stores or whatever where they can re-supply, but that's not an option where I am.

Done Camelbak Classic for years. It became one with me and can carry phone/mp3, gels, etc..

Done up to 24 miles with it. Forget stashing stuff, do you trust the weirdos in theis world? Forget the nasty t(cr)ap water and get good quality stuff.

As you deplete the fluids, the slight weight of the pack allows you to feel that much lighter and quicker which promotes a negative split pace.

You can easily determine mileage by going to this web site:
www.usatf.com.[/URL" target="_blank">

At the bottom of the page, you will see something that says: "find a running route/create your own route". Click on that. The next page will bring up a map of the US. Enter your Zip or City/Town. Then use the slider to zoom in to your neighborhood.
You can now chart running courses using your mouse to click along a route. Mileage will be accumulated on the left.