Well, firstly you need to consider tiers
In case you don't know, a tier is a ranking of a pokemon's strength (essentially). These tiers are Uber, Overused (Standard), Borderline (sometimes merged with UU), Underused, and Never used. You can't use any Uber pokemon in a OU team, no OU pokemon in a UU team, etc.
You have quite a mix.
Ninetales: UU
Salamence: OU
Alakazam: OU
Vileplume: NU
Magnezone: OU
Slaking: NU
This is not a good mix, since you can't really win in any category. The only category you can play in is standard, and with that team you won't succeed.
As Enkidu said, Ninetales is not a good opener. Whilst I am a fan of the pokemon, a shuffler can't really serve you as an opener. It can't really set up anything. The held item won't really do anything for you, it won't deal any real damage, and whilst as a pseudo-hazer it could serve you, I wouldn't use one as an opener anyway.
I can tell you got your Salamence from smogon, but using a Jolly nature really doesn't serve you. In fact, Jolly is -Sp. Attack and you have Evs in that very stat; why would you use a - nature on it? Either use Naughty (+Atk, -SDef) or Naive (+Spd, -SDef).
Alakazam looks great.
Vileplume & Slaking, get rid of them. Its not the movesets, its the pokemon themselves; they suck. And I mean they REALLY suck. Get rid of them asap.
Magnezone... well, I haven't used a Magnezone, so I wouldn't know.