Bicycle Tutor

I just purchased a bike that has a Shimano revoshift shifter. I am confused because the Left shifter, which would normally show three settings, has a range of L-H, with ten marks in between. Not sure how I'm supposed to interpret it. (there are definitely only three sprockets).
It seemed as I rode it home that nothing happened to change the chain until I'd moved it at least a few marks, and it wasn't really on one of the marks that it felt firmly in gear. I suppose I've just gotta keep experimenting, but if anyone has any additional info about these shifters, I'd appreciate it.
The video on shifting was very helpful BTW. I've never had a bike with so many gears, so I needed the extra help about combinations to avoid, etc.
Thanks,
Lise

Not sure, but I suspect that your left shifter is not really "indexed", meaning that it doesn't have three distinct clicks for each of the gears. Like older shifters, you twist until you go in to the gear you want. The 'ten marks' don't really mean anything. If the shifter just rotates smoothly without having three specific places it locks in to, this is probably what is going on. If so, it should still shift fine. You'll get good at putting it in the gear you want with just a little practice.
The only gear combinations you really want to avoid are large chainring to large chainring (front, back) and small to small. This forces the chain to run at a very steep angle compared to the chainrings and puts extra stress and wear on it. But you won't damage anything if you accidentally go into one of these combinations. It's more a long term wear issue.
In general, you'll probably leave the chain in the middle gear in front and just adjust the back one according to your speed. If you find you get to the point that the gear isn't high enough, switch up to the big one in front. Going up a steep hill, switch to the small one in front.
If you get confused, remember that the chainrings closer to the bike are lower (easier) gears, both front and back. Away from the bike is higher gears. Large in the front is high while large in the back is small - confusing, so sometimes easier to remember inside versus outside.

Yes, Shimano Revoshifters are not indexed so there is not a fixed position for shifting to each of your three chainrings. Low (small ring) may not require twisting the shifter all the way to the L-mark and similarly High (large chainring) may not require twisting all the way to the H-mark.
On my bicycle with Revoshifters the small and large chainrings are engaged one click before the L or H marks so that is as far as I twist the shifter for those gears. I have put a little piece of silver duck tape on the shifter to indicate the middle position where the middle chainring engages. This makes it easier for me to find that middle position when shifting to the middle chainring. Another guide is to count the clicks -- for example to shift from the large chainring to the middle chainring I have to move my left Revoshifter four clicks towards the middle.
You may find that in certain gear combinations the chain will rub slightly on the front derailleur. Because the Revoshifter is not indexed you can easily "trim" the front derailleur by moving the left Revoshifter one click in one direction or the other to eliminate the rubbing.

Just to be clear, the left (front derailleur) Revoshifter is not indexed. The right shifter for the rear derailleur is indexed.

Hey,
Sorry I didn't get back to this - Life has been getting in the way big time. Anyway, thanks for the info - you answered my question and I was able to work with it fine, other than my awkwardness with so many gears. and yes, the right shifter is indexed. Hopefully now I'll have some time to get out early when it's quiet and practice with those gears so I can feel some confidence with them. Been missing being on a bike : )

I don't want to sound patronizing, but if you want some good, basic advice on shifting all those gears, have a look at the "How To Shift Your Gears" tutorial on this site at:
http://bicycletutor.com/gear-shifting/
I found it really helpful myself when I first got a multispeed bicycle.