I assembled an army centered around a Storm Golem and some Altem Guardsmen. I'll probably face an army with many Troll Artillerists.

My question is: what can be done in a situation where both armies just sit waiting for the other to get into range?

Take the die roll tiebreaker,

or use harrasment so you know you can get the first shot in

I might be wrong, but I think that stormy has a range of 14" while the trolls have 12", this should ensure you a first shot at one of them. Or use harrassement. Shades could tie up all the arties but one that you will shoot with stormy. Then break with one shade or just let it die and repeat the process, just use the altem to take the place of the shades (plus altems can attack). Anything remaining should easily be dealt with with the rest of the army.

actually, if the Troll player do not want, you will not take it...

In fact my experience shows that Usually who moves into combat first takes the first shoot.. as if you move into the troll outside his range, and in of yours, the troll can just retreat.... and then, it starts all over.... Harassers make a huge difference here

Thank you all

I tried this plan today, but my opponent answered with Mortis Draconun, a Technomancer, and 2 artillerists (there were a few other pieces, but these were the ones that made the difference).

Everything was going fine up to the moment I went to harrass the trolls with the Guardsmen. My opponent got two very lucky shots (he was lucky before with excellent regeneration rolls) with the artillerists that effectively disabled them, and got the upper hand.

If he had missed, Stormy would soon make short work ot the Trolls. It was quite close in the end.