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Your topology isn't too bad! I have just three things to mention off the bat.
1) Look up nasolabial folds on wikipedia, they are more visible when you are older and are very obvious when you are smiling or yelling. In topology, it helps to have a line of faces running from the top of the nostril and hugging a little closer to the corner of the mouth so that you can get that deformation much easier. In the attached image, the blue line of faces should be about where the red line is. It may take a bit of work to get your faces uniform again though but it will be worth it.
2) Also to help deformations, you want the number of faces on the top lip to match the number of faces on the bottom lip. I would say remove some topology from the top lip rather than adding more to the bottom. It's not necessary, but it will make your life so much easier when you go to rig this. Same goes for the top and bottom eye lids.
3) Last thing is minor, it looks like from your image you don't have some vertices welded on your chin.
, thanks for mentioning that! I've really never thought about what you said on the 2), i will definatly keep this in mind in the future, when i think about it im pretty sure i've made the same mistake for the eyes of this character ... :p 
