(matt, your site sucks, it ate my first draft here. )
this is all stuff that works for me to get places, so take that with a grain of salt, cause "me" is a young white girl, so your mileage will vary.
*i have a friendly looking dog .. folks have picked me up time and again saying "oh, your dog just looked so cute and sad by the road there, i couldn't help myself, i have three dogs ... " i don't always travel with him, but he's more than contributed his share when i have.
*try to find some kind of balance between looking like a jehovah's witness and an axemurdering methhead crustie bum. most rides don't come from punk bands in tour buses, most are from pretty normal, prejudiced people. i usually rock the itinerant farmworker look - this seems respectable enough to get picked up in the midwest by even the most dour pentacostal woman, and dirty enough to get picked up by the freaks.
*try to look like you're actually having fun standing out on the side of the road breathing carbon monoxide. seriously. this is hard, though, when you're cold/hot/hungry/tired/staring into the sun for hours and have a migraine ..
of course, one time i got picked up out of pity when i was so miserable i was bawling my eyes out by the highway. maybe that won't work so well if you're a dude ..
*signs. make a sign for a town no more than 100 miles in the direction you're going. i get wayyyyy better results going places if i'm flying a sign for somewhere not too far, plus sometimes you get picked up by the person going 500 miles in your direction .. also, make your sign readable, and for crying out loud, spell the town name right.
*spend a minute to find a good spot to hitch - where people are going your direction, where there's enough time/space for people to actually see you and stop and pick you up. don't be afraid to ask around.
and there's always .. truckers. in desperation, check out the local truck stop or gas station on the end of town. talk to truckers there, see where they're going - and more importantly, if their carrier is anal about allowing hitchhikers. oftentimes i've been directed to people going my way, and even gotten the hideously creepy long-haul rides a few times. in my experience as a woman, every single trucker ride ends with the trucker at very least demanding sex in trade for the ride (do i just always get the lame ones?), but you might have better luck there.
i've pestered people at gas stations even, but the attendant will usually give you the boot pretty quickly, so try to be discreet if you do that.
anyway, i don't hitch much anymore, and i don't know why i wrote this all (and rewrote it even), but maybe it'll help. i-70 is totally doable. best of luck in your endeavours, and
-max