We headed over to Isle Of Man from here in the UK last September.
Travel method in our case was by the Manannan sea cat from Liverpool to Douglas and back - www.steam-packet.com
Research for the visit was largely done by taking a look at the official Isle Of Man tourist website - www.visitisleofman.com and by getting hold of a copy of Lily Publication's Isle Of Man guide.
We found our accommodation via booking.com and whilst it was an okay B&B, we could have made a better choice...
We didn't hire a car at all for our stay.
We bought the six day Heritage Travel Card which allowed us to use buses, trams, steam trains and the Electric Railway to get around the island and to visit many of the heritage sites and museums too.
This card allowed us to visit Laxey Wheel, Peel, Port Erin, Castletown and Ramsey during our week on Isle of Man and to get to the summit of Snaefell too.
Eating out in Douglas was largely done in local pubs such as The Queen, The Prospect and The Bridge along with Ciao (pizza) and Tandoor (a good curry house that was frequented by both locals, visiting building workers and other tourists too).
Lunches were usually taken at cafes or pubs in whichever town or village we were in at the time - apart from in Peel where we ate outside at the kiosk down by the harbour wall - if you do go for a hot kipper bap, have some baby wipes to wipe your hands after consuming said bap!
Weather over our time in September was changeable - one full day of t-shirt weather then a mixed bag of clear windy days and downright rainy days too. We travelled hand luggage only, but had our mountain waterproofs with us along with fleece tops, hats and gloves too.
We had a great time, despite the weather and it was only the cost of the ride that put us off going on a motorised trike around the TT course. We did cross the TT start/finish line on one day out, but that was on a service bus!
What we did notice was how friendly everyone was on the island. People stopped to ask us whether we need help in finding our guest house or somewhere to eat and were fairly chatty in pubs, cafes and shops.
Hope that this helps with your quest!
Enjoy... we did, despite the weather.
PS Apart from the TT races, there's also the Manx Grand Prix road races too - held in late summer.