One thing you will find throughout Tajikistan is an immense spirit of hospitality. As much as you may want someone to help you out in any way possible, there is often someone right there who will be able to do so, often for no charge.
Since I don't speak a lick of Russian, nor Tajik, I was a bit apprehansive about arriving in Dushanbe at 3:30am and not having a guide there to help me arrange my first day there. I had some relatively complicated plans that I had to arrange once on the ground, and felt a local guide would be best in making it happen.
There are some websites for small tour companies who will provide you with guides, for a relatively hefty fee, though. Not needing a guide who would drive me around and show me things, I asked the Pamir Lodge in Khorog if they could help arrange a guide for me in Dushanbe (as I was already planning to stay at their lodge when I arrived). They said it would not be a problem, and gave me the email of a relative in Dushanbe who could help. No matter how many times I asked, though, he would not give me a price for his services.
Upon arrival, the arrange relative met me as promised. He spoke excellent English, and dressed even better. Apparently he had just come from a nightclub with his friends, who were all sleeping in the airport lounge. We talked, he bought me tea, and then we started to plan what I had to do in the next few hours. Like most people there, he went out of his way and arranged everything for me. So, a few hours after meeting him it was time for me to go. I asked how much the time he spent with me would cost, and he refused payment. Despite flashing him some money and begging him to accept anything from me, he refused.
So, if you need a guide in Dushanbe, or anywhere in Tajikistan, start by asking your hotel. If you have as good of luck as I did, they will set you up with a relative who is in no way trying to rip you off or make money off you.