Outer Game is another gigantic subject. Topics regarding the Game will usually be spit into inner or outer Game category.
Let's start with an easy subject. Outer appearance.

Unfortunately people judge us (and we judge them) by appearances first. But that is normal since we don't have any other information we can work with. This is why appearance matters. Not a lot, but it helps. Game is consisted of many small parts that add together.
If you are new to the Game, you are probably not a fashion designer and don't know much about fashion. That is OK. You will learn.

First stop your mother dressing you! Or stop dressing like your mother would dress you (or (ex)wife). It is easier when someone else dresses you but you are not a kid anymore!

What can you do?

You can copy others. You don't have to reinvent the wheel. Copy those whose style you like AND who are considered cool. Dress stereotypically. You want to use positive stereotypes. If you are a business man dress like one (but a cool one). If you are a rapper, and live for rap music, dress like one.
Go to the night clubs and see what are "cool guys" (those with hot girls) wearing. Copy.

I know what are you thinking: "This will cost me hundreds of $$ (or €€)". No it will not. There are a lot of affordable shops that sell currently cool clothes. I personally don't like online cloth shopping, but am considering it more and more. Look for great deals, you don't have to buy everything now (for time being buy one cool outfit you can wear when going out). You don't have to wear brands (although it will not hurt). Look at your cool friends. Ask you female friends to help you out (go shopping with them).

Clothes is one of the first things where your friends will notice the change. Don't get provoked or discouraged. They will get used to it. I was called "hipster" or "gay" on more then one occasion, but as long I am getting my share of girls (Game slang is HB - hot babe), I don't mind.

When you have found out what style suits you, experiment. Don't be like 99% of other guys out there (and you probably won't be because you copied the "cool" guys). Try with different stuff, the stuff you didn't even dream trying a couple months ago. It will look strange (at first), but give it enough time and ask others (girls) what they think about it. You will notice their responses are not as bad as you thought. Being different sets you apart and that is one of the aspects of the Game you want. People in any social event are in one of two groups. They are either observing or being observed. You want to be in the second one. Those being observed are perceived as leaders and their social value is high (more on this topic later). People want to be in their presence. They are "interesting" people. Try thinking about one of your friends, colleagues or acquaintances who is considered interesting or cool by you and your peers. That is who I am talking bout.

But to get back on the subject of clothing, here are some fresh general rules.

Clothes is one thing where you can relatively fast achieve good results. Another is hair and beard.
Regarding beard, there is one easy tip for begging: loose it. Just that. When you find looks that suits you, please be free to experiment. But until then, beard usually looks creepy.
Regarding hair, there is no rule, as long as it is tidy and orderly. If you have no idea, go to your regular dress salon and let your hairdresser experiment. If you still don't know, go to one of those 50$ hairdressers and when you get the hairstyle you like, go to your regular and show her (him?) what you want.

Third part of the equation is your body. This one takes more time. "In healthy body, healthy mind". If you are not satisfied with your looks, do something about it. Hit the gym and change your diet. I am very against diets as food reduction, I am more for start using more calories (aka the gym) and split your meals to more smaller ones (I tend to have 5 or 6 per day). This way I am never hungry but I also never overeat (it is all about self-control which is tough).
One of biggest mistakes I made when I started changing my body was a heavy food reduction). I reduced all my meals to half (back then I had 3) and cut off all sweets (plus regular exercise). I lost 20 kg in 3 months. That was not healthy. I am having much more trouble now when I am trying to gain muscles (which are heavier then fat, FYI). I should have just split the meals and started eating healthier while exercising.
Today, I try to watch what I am eating. That doesn't mean I will not go to MacDonalds, but will try to avoid it if possible. I also try to eat a lot of fruits, vegetables and meat, reducing fat as much as possible. With all that I go regularly to the gym. I am no gym junkie. I go alone, so I had to find a way to motivate myself. One thing that works for me is to go to the gym which has regular fitness programs (e.g. crunches). That way I have "an obligation" to show up at specific time. It gets me started, so going to the rest of gym is not that big deal since I am already there. I also use audio books to keep my mind busy while exercising (repetitive work is boring).
I am happy with the results but there is always area for improvement. This was the first summer I was happy showing my body (I was always a chubby kid). And I can't describe you the feeling first time I wore a slim shirt. It was worth all the work (and suffering). I am also a lot healthier and have more energy. I rarely get sick. My allergies are almost gone (and as kid I basically could not breath starting in February and ending in November). If not for anything else, do it for your health.

Here is a great link that thought me a lot.