The best time of year for seeing dolphins in the Moray Firth is generally from May through to September. Though they can be seen at any time of the year they tend to drift down the coast to areas around Aberdeen.
The best place to see them is undoubtedly Chanonry Point, near Fortrose. The best time of day to see them is from low water onwards - in my experience around an hour or two after when the tidal currents begin to swirl around The Point - this will virtually guarantee sightings of dolphin.
Very low tides are particularly favourable - It is a matter of luck if the dolphins start to perform - when they do, this is frequently within yards of The Point - and I mean yards, so close that you will hear them blowing!!
The boat from Avoch is in my opinion very expensive - around £15 for an hour, much of which will be spent going the few miles to and from The Point. Save your money and stay at The Point - and the views are invariably better.
A mate of mine - Charlie Phillips works for the Whale and Dolphin Conservation Society, and he spends a great of his time - much of it around The Point, taking photos by which he and his team are able to identify individual creatures. During the summer months he runs a blog, and it is here that you can get a general idea of the current activity.
http://www.adoptadolphin.com/blog/
Taken from the beach at Chanonry Point ....