What I do see:
--Decent posting size: You don't write one liners or two liners, so you give a fair amount to work with, I do like this
--Fairly good knowledge of cannon lore and limitations. This is pretty good from what I have seen. I like it
--Bulk posting: Its kinda hard to follow your text sometimes because you don't really use paragraph breaks. That "Enter button" is on the keyboard for a reason and it can make your writing seem a lot more elegant as well as show a change in idea.
What I'd like to see:
--Character. Sadly your John Sheppard seems to lack a lot of Character motivation. I want to know what makes him human please. I love this part about role play and characters. Don't shy away from this.
--Noncombat: Waving a gun around is pretty dandy, but that's not who a person is. I'd like to see who John Shepard is, not just a fellow with a gun.
--Paragraph breaks.
--More descriptive words. Adverbs and adjectives paint the scene, they tell us more than actions ever will. Eg: there is a huge difference between:
1) "He sighed"
2) "he sighed irritably"
3) "he sighed wistfully"
See what I mean? Whole 'nother world.
--More body language: Body language is the key to the mind, we communicate more with unspoken than we do with spoken.
You have got a great start and I am looking forward to where you go from here. Cheers!