Well, start with some simple changes to your diet. No need to go crazy all at once.
1. Only drink diet soft drinks.
2. Drink coffee and tea black or with sweetener
3. No desserts
4. No chips
5. No french fries at fast food restaurants
6. Chew food thoroughly
7. Lots of protein
8. Use smaller plates if you have some
9. Always choose the vinaigrette dressings
That will last for the rest of your life.
Once you've gotten used to that for a few weeks, then look into a little more control over your diet. Cutting calories, slashing carbs, etc.
This is more or less how I started my weight loss journey (except for black coffee, gotta have some milk in my coffee). I cut out all junk food and sugary sodas,, and I would take a 20-30 min walk every day for about 2 months. I even made a rule for myself that I didn't allow myself to play videogames that day until after I had my walk. After about 1-1.5 months of just doing those simple things (cutting out junk food and taking a walk each day) I joined a gym. I was lucky that I had a gym that was only 5 minutes by foot from my apartment (granted now that I've gotten more serious about lifting weights I've switched gyms since the first gym's equipment was pretty bad).
After 2 months I started getting my diet in better shape. Even without junk foods and sodas and exercising I was still not losing much weight, and it would spike up and down a lot. Don't weigh yourself everday unless you are ready to see your weight go up and down a little and can handle that. It's easier to weigh yourself at the same time of day, same day once a week. Nowadays I weigh myself every day but I'm able to handle it now.
In hindsight I maybe should've gotten a better handle on my diet before starting working out, at the time I didn't know that weight loss is 90% diet, but whatever path you take stick with it. I eased myself into a healthier lifestyle gradually, by first just cutting out junk food and taking a short walk each day, then joining a gym, then getting more serious about what I eat.
I started January 2011 at 165.5kg (365lbs) and was fed up with being obese and seriously out of shape (walking 15min into town would leave me really out of breath and sweating a lot), today I'm at 117.8kg (260lbs).
There were times when I fell off the wagon, sometimes day, sometimes a week, and once a whole month. The important thing is to stick with it long term, it's a lifstyle change that should last your whole life. It's not a quick fix that will only last a couple months and once you've lost the wight you go back to your old habits. My old habits are what got me to a fat sack of lard weighing 165.5kg, and I don't ever want to go back there again.
Sorry for the wall of text
Just felt like sharing my weight-loss journey so far.
Pics!
Don't have many pics of me from that time, this one is from January 2011 when I was 165.5kg
(ignore the clothes on the bathroom floor, my roomate left them piled in front of the mirror so I threw them down to take that pic)
Today at 117.8kg
Still got a way to go (my goal is to get below 100kg for the first time in almost 8-10 years), but I know that I'll get there eventually.