1. check out your own talent build see if it's more towards pvp or pve direction, and check if you have your spells keybinded/macroed, if not, do it right away. I know it's different now in mop than in cata, but sitll you should be doing this as you're expecting to win more
2. Please play over 1000 arena games( 2s and 3s to be more specific, 2s might be more suitable for pvp beginners who are still need to learn what capability of every other classes, and what are the "left out" spells could you be using in certain situations)
3. Check out the big names for your classes as well as other classes. A good pvper(a multi seasonal gladiator or at least 2.2+ arena player) can often inspire you in terms of macros/keybinds/play styles and etc. Check their armory and bookmark them in your browser and re check them once in a while see if they're making any chenges in terms of geming/ enchanting/ trinkets/other useful gears/a specific weapon/ professions.
4. Do duels while waiting for queues, it also helps you to understand/study what are the new spells other classes have now in this new expansion, and thus have a better prediction on when they're about to use them and what/how/when you should be using your spells to counter.
5. You can queue with a premade for random battlegrounds. However, individual abilities still counts even if you're in a premade. I've seen/experienced premades got owned by the opposite team simply because we/they outplayed them/us. Please do realize every move/every second counts.
6. If you have entered in a middle of a game while your team is being camped at graveyard, or 0/2 flags. Please do not quit immediately, instead go out there and try as hard as you could to change the table, if you failed to do so, please don't feel bad about it but be proud of yourself. Because it could be an another way to gain your confidence if you happened to have some blow kills even in that sort of tough situation. If you're a healer, try out-heal all other healers. If you still lose that game you should still be proud of yourself because you've done what you could have done.
I hope that the complainers actually read through my advises and be benefit from them because that's how I play pvp. In my case, I failed to reach 2K+ in my first arena season and I'm not complaining anything but only have realized how hard pvp can be if you're looking for competition in a rather high rank, and I have only learned how to do better when situations getting tougher.
I do not have any proud pvp achivements but I sincerely believe that making efforts on your own is always better than making a thread complaining how alliance/horde always lose lose lose in random battlegrounds.
Making threads about how you lose every single game on this forum is only meaning admitting that you're bad, you're one the problems for your faction/team, and arguing with other people when they analyzing your problems or giving you advises only explains why you're still bad: you do not listen and do not want to learn.
Here are some of my random battlegound stats(just a bit of a prove that I'm not some random garbage player that suck really hard in pvp but thinks he's a pro):
Battlegrounds played 3,540
Battlegrounds won 2,152
Random Battleground win rate:60.79+%
Arenas played 909
Arenas won 597
Highest 2 man personal rating: 1761(I didn't play many 3s for my first season simply because I realized I wasn't really ready for that much of details in 3s as a disc priest)
In arena there're too many things to be considered, such as positioning, timing, mana managing, etc. and when you getting used to pay so much more attention to every details then you'd carry that good mindset to every single random battleground you play in, so it's predictable that you'd have a better random battleground win rate in a long term.
P.S: If you just going to ignore all of the above than I think you do not have the right to complain about losings because pvp is like everything else in life, it takes efforts and it takes time to get any better.(not even consider being really good)