It depends on your routine as to what approach you will need to take. Body builders use a "slim down" technique right before competition that, slightly modified has kept me nice and lean.

In essence right before competition they eliminate all fats, except omega 3's, from there diet and stick largely to carbs. If you get rid of all dietary fats being consumed (for the most part) your body will consume internal fatty deposits.

You need to get rid of red meats (all) and dairy products, also nuts and fatty veggies. This diet cannot be maintained for long periods as its not designed for wellness overall. But you well lean down over the months used.

You can allow yourself a "splurge" once a week, ice cream or pizza/steak, but it must be only on a single day. For the rest of the week you must stick to the no fats along with eliminating caffine, salt, NEVER ANY PROCESSED FOODS. PERIOD.

Have as much rice, noddles, legunes as you want. Chicken and fish too. Sugar should be brought to  as low a level as you can tolerate. This is what I have been using since June of last year and my size and weight are easy to control. You must institute some form of aerobics to maintain proper metabolism. Hope this helps.

To get huge you you would need a combination of working out with heavy weights,genetic potential,and maybe steroids,so do not worry...you won't get "monster"huge if you don't do these things.
Not going to a gym means you buy your own equipment or you rely on good exercises like pushups,pullups,chinups,dips,crunches,etc.
You can buy a set of dumbbells and add weights as you get stronger,thus not having to make a large investment at first.

Spread out your calories throughout the day.Instead of three large meals,eat 5-6 (300-400cal each)40%protein;20% good fat(CLA,omega 3 and 6,etc),40% carbs(preferably complex carbs that breakdown slowly and never after 7-8PM).You want to keep you blood sugar at a level that does not increase your insulin levels too high,except after working out hard to replenish your energy and feed those muscles you just stimulated.
DRINK AS MUCH WATER AS YOU CAN!I am talking in the range of 8-10 16oz glasses/day.Keep your urine colorless.If it is yellow,drink more water.
Add aerobic exercises(running,ski machine,bicycle,skates,etc)to burn calories.
Losing weight is accomplished by expending more calories than you take in,but you don't want to diet because you want those burned cals to come from stored fat,not muscle.
check out these sites for workouts,dietary plans and motivation!
[url]www.musclemedia.com[/url]
[url]www.muscleandfitness.com[/url]
Good luck and let us know how it goes!