First of all, I would like to say that if you are not willing to do so much as "Do something complicated" to get into a clan... You're respect points drop considerabley. But if you really want to get into a clan and you are willing to do so much as read the post, then you have at least a step. Rellly its not that complicated. Just say why you want to get in (and not because you have been wanting to get in XD ). After which post some things about yourself in toribash, such as what your favorite mode is, what you specialize in, and how you fight. After which you should demonstrate your skill by posting replays.

EXAMPLE

Hey, I have been wanting to join RA for a while, I like how you focus on wushu and how you promote relaxed fighting. I myself (obviously) fight relaxed and love wushu, I usually try slightly out of the way moves like punches and counters, I like to think I specialize in wushu, but you be the judge ;)
Here are some replays of me proving myself in SP and MP
REPLAY
REPLAY
REPLAY

I hope this helped ;) took a while to post but hopefully it will give people an idea of what to do.
NOTE: you should read the clan rules to any clan you are even mildly considering, maybe you're an 11 year old in a clan that promotes people 15+, maybe you are a potty mouth in a clan dedicated to good spirit.

Read the posts ?
As SnoflakeG Did
EXAMPLE

Hey, I have been wanting to join RA for a while, I like how you focus on wushu and how you promote relaxed fighting. I myself (obviously) fight relaxed and love wushu, I usually try slightly out of the way moves like punches and counters, I like to think I specialize in wushu, but you be the judge ;)
Here are some replays of me proving myself in SP and MP
REPLAY
REPLAY
REPLAY

Huh... I don't have any replays of me fighting, I don't wanna go thrugh a pile o sit to join, and I like cheezeburgers.

YOu really do need replays, Sahee usually really stresses replays :/ If you dont have any make some. Sahee as has said, doesnt take kindly to people who don't follow the first post. +doesn't make a good first impression.

If you
then don't join.

As above, what I just wanna add is - don't join at all. Ever. Just disjoin and live like that. No, you know what? Just disjoin before joining and die o:. Or better yet: just die.

(Translation:
if you're stupid enough not even to read the first post on this page, the post right behind your lazy ass' post, treating about how to post, then your post is not "posty" enough. Did you get that through all that posts treating about your post or should I continue to post about your posts till you die of overposting or being overposted? Dude. Watch what are you doin' o:!)

Oh, some think I love making such posts... ;P
But hey, how could you tell?o:

Sahee u r killing that guy xD
I bet he has the thoughts of suiciding

*sings* Cause they all deserve to die,
Tell you why Mr Donkor
Tell you why.

Because in all the history of human race Mr Donkor
there two kinds of man and only two.

There's one standing put in his proper place
And the one with his foot on the other one's face.

Look at me Mr Donkor look at you.

Me r Donkai ! xD
Me want seeng tho =(
Me like me like me like RA
Like me like me like me RA
Love me Love me Love me RA
**ck me **ck me **ck me RA!

No, we aaall deserve to die!
Even you Mr Donkor, even I.

Because the lives of the wicked should be - made brief!

For the rest of us living,
death will be a relief

Yes,
We all deserve to die!