Salam dewana tera jee,
The best medical college in Pakistan is, in my opinion, Aga Khan University Hospital in Karachi. It is very competitive. There is also King Edward medical college in Lahore and DOW medical in Karachi which are also excellent.
The atmosphere in government and private colleges is very different, and the atmosphere in government colleges depends on which city they are in too. There is things like the teachers never being there for lectures, student politics and absence of lab facilities etc in a lot of govt colleges.
There are government colleges in a lot of cities like Peshawar, Rawalpindi, Jamshoro, Sukkhar, Larkana etc, (I think), and some of them are not so competitive but that have their own specific admissions criteria.
Then there are many other small private colleges, which are not that competitive to get into, for example as Zakk jee mentioned Hamdard, Baqai etc in Karachi.
The criteria for AKU is merit and it is a little bit expensive. For government colleges, merit and contacts are both useful I think. Then for private colleges, minimal merit but ability to pay is required.
Most people go to medical college in Pakistan after doing Pre medical in FSc, or having passed A levels with biology/chemistry, that is basically, after high school level. However, I think separate colleges have separate criteria.
Your best bet would be to do a lot of web searches on google.com and go to the homepages of whichever medical colleges have websites and gather info from there. They alo might contain email addresses of current students or alumni whom you could contact and gather info from.
Best of luck. Feel free to ask any other questions you might have and I will try to answer them to the best of my knowledge inshallah, though I must admit I am no expert.