You can reach Yaremcha by train:
606 К Lviv – Rahiv (львів – рахів)
Departing at 15.20 from Lviv and arriving in Yaremcha at 21.03 (Rahiv 23.58)

606 Л Rahiv – Lviv (рахів – львів)
Departing at 01.22 from Rahiv, arriving in Yaremcha at 04.15 (Lviv 10.10)

As you can see there are very few trains which operate on the Yarmecha’s route.
In winter is possibe to find more train but i can’t say it for sure.

Anyway if for example you came from Kyiv, or other cities not so close to Lviv, the best way to get there is through Ivano Frankivsk.

You can reach Ivano Frankivsk by train there is a plenty of train which goes there from almost every city.

(Ivano Frankivsk’s railway station)

Then right out of the railway station, you will find a large number of busses and mashrutkas, you will not have much problems to find the one with the sign YAREMCHA or ЯРЕМЧА. (photo below)

The bus will bring you to the bus station of Yaremcha. (photo below)

From there you can easily reach your final destination by taxi or even by feet.

For to know about Yaremcha Bus timetable:

http://en.ukrlandia.com.ua/yarmecha-timetable

There photos were taken during the last summer (2008) so the timetable may have change.

How to reach Yaremcha

http://en.ukrlandia.com.ua/yaremcha