A bell is an essential. I know they can seem a bit dorky, but if you ever plan to use the multi use paths, while shouting is often required for some. A simple few tings with your bell will alert most pedestrians.
Initially your body will need to get used to cycling. Recommend max 1 hour per day, but most important is to ride and gradually build up distance and keep riding. Keep it fun, ride different routes and set yourself achievable goals. The worst thing you can do is push too hard, obtain an injury that stops you riding for a while. Don't worry about numbers, don't stare at a cycle computer, just ride for the fun of riding even if at times you'll be sweating buckets while wishing you had more lung capacity to breath and asking yourself 'what the heck am I doing this for'.
Remember that cycling is part of a life style - Cycling won't 'magically' make you lose weight. Good diet goes hand in hand with exorcise, but because you'll be cycling more you'll be able to give yourself the odd treat as you'll most likely burn most of it off on your next ride.
Put on your best amount of willpower because there are going to be some days where you are really not going to want to ride, but often if you can push through these mental blocks you'll feel better afterwards.