Hi there,
For the past two years, I have gone to the Migration Advisory Office (Fachstelle Migration) in Zug, where they will complete simple tax returns for 70 CHF (you need to pay an annual 'membership' fee of 10 CHF first). They're very friendly and have some English-speaking staff. I've never had any problems with the tax returns they have filled in for me.
All their details are here:
http://www.zug.ch/behoerden/org-mit-...dvisory-office.
You can just walk in during opening hours and they'll have a chat with you and give you a checklist of everything you need to bring, which depends on your circumstances (statements, wage slips, etc). You can then go back another day and drop all of this off. Once it's done, they will then post your completed tax return to you (along with all your documents), in order for you to check and sign it and send it off to the tax office yourself.
Best of luck!