There are several tour companies that cover all things Loch Ness, from day trips to multi-day tours through the Scottish Highlands. On these tours, you can choose to travel from Edinburg to Loch Ness, or else you can decide to stay in one location around the immediate area for a few days. Some tours offer a free bit-of-whisky to help prepare you for your monster search. Hum, I am guessing it's possible to see a lot of monsters after some of the lovely whiskeys Scotland is known for.
If a tour trip is not what you prefer, consider a Loch Ness cruise aboard the Royal Scot. We love their description on their website. "Mad about Monsters? Then our daily and evening Loch Ness cruises are for you! Our live commentary will take you on a journey through the local history, nature, and local folklore of Loch Ness, including a presentation of our onboard hi-tech Sonar equipment to help you peer into the depths to see if you can spot our favourite monster of the deep, Nessie! You may even be as lucky as our very own Operations Manager, Marcus, who recently won £1000 in a photo competition for the best sighting of the Loch's famous inhabitant - Nessie!"
Based on their description, they sound like a fun group. Check out their website for the entire ordeal of the operation manager. I like that they have onboard sonar equipment for the search instead of just being a regular, over-the-water hunt. Either way, if you see something or not, this would make a memorable sightseeing cruise.