You know their name- as you can see this isn't really a level as it is 0. Here you have maybe met them in passing, ie only introduced and you for some strange reason remember their name. Note that it is awkward to stalk them and get their phone number, that is only acceptable in later levels. Plus the stalking may be complicated by the fact that you know so little about them- this should be a hint, take it!
You know more than their name, ie you had a conversation with them, it can be as part of a small group (3 or 4 people) and you learnt something about them that makes it a lot easier to stalk, or even better you got their number after the conversation, this may in itself be jumping the gun a bit. Note that I said it makes them easier to stalk, I did not condone it or say that you should and hence you may not get their contact details off the facebook, it is however acceptable to add them as a friend if you have more than 1 friend in common.
I think it is important at this point that this is not based on anything other than my experience and it is by no means the only way to make friends and be less socially awkward, but the idea is that it is a healthy guide.
You have had a one-on-one conversation with this person. it doesn't have to be long or deep or anything but it has to be on the two of you. This also gives you the opportunity to get the person in question's number if that is how you operate. Note that here the line is fuzzy as guys will probably not exchange numbers so easily with other guys whereas girls would. It is important that the number conversation happens whilst in a one-on-one conversation as this ensures that you can be turned down without too much embarrassment to yourself or the was-to-be lever 3 friend.
You message each other and hang out from time to time, lets say on a fortnightly basis. The conversations are still light and generally everybody is having a good time. It is not a bad idea to stick to this level for a while if you have the choice to do so as you can learn a lot from a person in these casual meetings. Suggested time in this level before making a decision is 2 months, although you might not have a choice in the matter as level 4 can happen due to factors out of your control.
This is classified by more of level 3, ie more hanging out and more messaging. There are however a number of other way in which one can get to level 4. One of these is when something memorably awkward happens. The best is example is what happened the other day with a friend on mine. She had this thing on her lip and I had to tell her- your lip is oozing... whatever level you were on below 4 you are no longer on- There is no turning back from here- these things happen and yes they might be awkward but in some way humans are still animals and priceless moments like these are never repeated and will definitely take it to the next level.
Have a deep conversation, nothing more to it.
Now I think I'll stop there are the lines kinda get blurred with different types of friendships at this point, with guys and guys being friends as well as bromances and the like. Once again, this is my opinion and since it is my blog i am entitled to give it.
People do tend to skip out on levels and stuff but then what are rules there for if not to be broken, sometimes it is better to not break the rules though.