Did the portion from near Baynes Lake to Elko-Fernie-Pincher Creek-Waterton Village-Glacier-Whitefish this summer as part of a loop from Whitefish that also included Whitefish to Euereka, which I assume is part of your plan.
In random order:
1. The campground at Sparwood is nice. Free firewood and nice bathrooms/showers. And there is a great grocery store in town.
2. In Coleman (AB), stop at the cafe that's in an old Church, even if only for a look.
3. Heading to Pincher Creek, when you turn off P.R. 3 onto Rte. 507 I think it is, be prepared for huge rollers almost all the way to town. Don't miss the Burmis Tree on the opposite side of the road just before the Jct. with 507.
4. Pincher Creek is a sad little town. Never saw the campground. Got a motel because the town was flooded from several deluges. If you need groceries, stop at the mall on the outskirts.
5. IMO, the towns between Sparwood and Pincher Creek are best past by when looking for an overnight.
6. You will probably have a lot of traffic on P.R. 3.
7. The Park Cafe in St. Mary has great pie.
8. When you get to Logan Pass, do the relatively short hike out to Hidden Lake. Gorgeous view and usually lots of goats wandering around.
9. Note that Galcier is celebrating its centenial this year, so expect crowds. There will also be ongoing road work that might result in waits on GTS Road. Check the Park's web site for updates.
10. On the west side of the pass, Sprague Creek Campground is nice and has $5 hiker-biker spots. Lake McDonald Lodge (check out the room with the trophy heads then grab a beer at sit by the lake) is less than a mile walk from Sprague Creek. The grocery store leaves a lot to be desired. Treat yourself to dinner.
11. Definitely follow the AC map heading to Whitefish. Don't be tempted to shave miles by staying on U.S. 2. Heavy traffic and no shoulder in places. The AC route is nice, and the unpaved porton is manageable.
12. Same advice with respect to Whitefish-Eureka. Get off U.S. 93 where shown. Little traffic and scenic. Go the .25 miles into Olney to see the neat old store. When you get to Fortine, go to the bathroom at the Conoco even if you don't have to go. You will go from one world to anoher.
I did the Northern Tier between Seattle and Glacier in '99 and '00. If you would like additional advice/opinions about that portion, send me a personal message. Don't want to bore others.