I work part-time as a personal trainer and I can tell you that there are no quick fixes. Unfortunately there's a lot of bad information out there so a lot of people get lost in the beginning. As well, a lot of people will post what worked (or what they think worked) for them personally but it would not work for someone else. There are a lot of factors to consider - what shape are you in now? What are you eating? What are your goals? What are your genetics? How much time can you put into this? What facilities and equipment do you have access to? All of these have to be taken into account. So when I see someone say "Just do this and you'll get (insert goal here)" I automatically discount it.
If you get information from an educated, reliable source which is put into a structured, progressive plan then you'll be a lot more likely to get to your goals. There are no easy answers. Will doing an hour of core work a day get you a six pack in two weeks? For most people the answer is no. Will eating more mean that you will add size? Likely the wrong kind of size (gut!) if you aren't eating the right things. Will doing weights give you bigger muscles? Surprisingly, the answer can be no if you aren't doing them properly, in the right order, or with the correct resistance for your goals.
Sorry to be a downer but I see a lot of people get discouraged not because they're doing anything wrong but because they were given bad or unrealistic advice. Most men can add a half pound of muscle a week if they're doing everything right. Get a good, structured progressive program designed for you personally and get good advice about what to eat and you can put on the size without the fat. Work those muscles twice a week to failure, and by that I mean real failure, not what you *think* failure is (there's a difference). Find out the proper order for exercises (don't exhaust smaller muscles first which will stop you from growing the big muscles) and change them every four weeks. Make sure you're resting properly and most importantly make sure you find out the proper form and technique. Not only will you lower the risk of injury but when you're using proper technique the gains you make will increase tremendously.
Okay, lecture over...