Hey guys...

Jordo!

Religiously count calories that you presently eat. Now reduce it by about 20% and stick to it. Start there, modulate up or down as needed.

You can find calculators on resting metabolism, but really, there is considerable individual variation (and these formulas were developed when Americans were far less sedentary...), so unless you can find a place that does the respiration test, just assume whatever number you arrive at when making calculations is probably an overestimate.

We are not so different from our ancestors 400 K years ago... but we are far less active and have agriculture, so we eat tons and tons of crap while sitting on our asses, even though we evolved to run around with not too much food. So, as compared to our ancient ancestors, modern humans tend to have less dense bone mass, less muscle mass, and are fatter. Oh, and then there's all the diseases directly tied to diet like late onset diabetes and heart disease...

Cut out anything that is mainly fats or sugar entirely (e.g., cheese, whole milk, white bread, soda). No booze, if you are really serious.

Drink more water. Lean meats, fish, fruits, veg. Go easy on anything that requires some form of processing before it can be eaten (e.g., wheat and rice products, anything deep fried...).

Begin a workout regimen. Start with the basics if you are out of shape; stretch, push ups, crunches.

Run. Seriously, run. As you get more fit, add some wind-sprints to it (full tilt, short bursts).

Track everything you do and eat in a log. Note progress in strength (e.g., can now do more push ups) and weight (a few lbs every two weeks or so is reasonable if you stick at it -- and it tends to drop off quickly as first if you are really packing too much excess fat).

Picking up a set of body fat calipers or a decent scale that can estimate it is helpful as well.

Log everything -- humans are bad at estimating without record keeping.

Good luck!

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