I've been doing relatively little PvP these past few weeks, but it's been on my mind today and made me remember this post, which has been sitting unfinished in my drafts folder for many months. Might as well finish it!
I try not to hold it against people in my random warzones when they aren't too great at PvP. Things like knowing when to use all of your abilities and how they could possibly be countered by other classes are something that takes a fair bit of play time to really internalise, and that's not even getting started on the benefits of good reflexes, which not everyone has either.
However, I'm always astounded by the amount of people - even players who are actually quite good at the actual PvP part - who are completely oblivious to basic tactics in the objective-based warzones. So, without further ado: seven ways in which you can help your team win an 8v8 warzone, regardless of your actual skill at PvP:
1. Inspect your team at the start of the match
Obviously there are situations where this isn't feasible, such as when you get back-filled into a match already in progress, but in most cases you'll load in well before the start of the match and can take a moment to familiarise yourself with the rest of your team. I don't mean that you literally have to hit "inspect" on every single one of them, but at the very least you can check what sort of class and role mix you've got.
The removal of stances and cells as visible buffs has made it harder to identify tanks and healers than before [note: the fact that I even thought to mention this tells you how frickin' old this draft is], but at least at 75, looking at their gear and any set bonuses usually gives them away. Many healers also like to spam heals in the spawn zone as a sort of non-verbal way of saying: "Look at me, you have a healer on your team!" At worst you can still check everyone's advanced class and hazard a guess. If nobody on your team is even of an advanced class that's capable of healing, you'll just be showing your ignorance if you complain about a lack of heals later (for example).
2. Mark enemy healers
In a similar vein, the moment you come face-to-face with the enemy, try to take in the class and role composition of the enemy team. People who intentionally dress to confuse (e.g. bounty hunters in Jedi robes) can make this tough for new players, but you'll soon learn to recognise each class by their weapons and certain signature moves. If you see someone casting healing abilities, it's generally a good idea to put a mark over their head to make sure everyone knows who to focus on if they ever want anyone on the opposing team to die. (Plus if you're a damage dealer, follow your own advice in terms of focusing!) Try to resist putting marks on non-healers, because nobody really cares if that Juggernaut is your personal nemesis, and it's just counter-productive.
Close inspection of the enemy can also lead to other surprising revelations...
3. Focus on objectives
You could argue that this point is a bit of a "duh", but based on the number of people I regularly see ignoring all objectives it clearly still deserves to be highlighted. Aside from completely new players who might not yet understand what's going on, you don't really have an excuse. Even if you never looked up any sort of guide, the voice-over at the start of each warzone still tells you what needs to be done to win, and you should focus on doing that. Don't chase kills in random places, but rather make sure that you're always attacking an enemy position or defending a friendly one when you're in a node-based warzone, and stick with the ball when in a Huttball match. Depending on your experience level, you could also look up guides for each map on how to hone your objective play further and improve yourself that way.
4. Communicate
Nobody joins a PvP match to chat, but a minimum amount of communication is generally beneficial. Most importantly, it helps to call "incomings", such as when one or more enemy is about to attack an objective currently held by your team. It's fine to keep it short and snappy here - most people will know what you mean when you say "1 inc snow". (Confused about how people call directions? This post might clarify some things.)
I had this ancient screenshot saved under the file name "How to make calls in warzones".
Also, try to stick to being informative instead of being demanding or lecturing. When you're with a team of strangers, your odds of successfully playing battlefield general - even if well-intentioned - are pretty low.
It should go without saying that you shouldn't waste time ranting about how your team sucks or anything like that. I absolutely understand why people have that urge sometimes, but it does nothing to help - rather the opposite: it can cause newcomers to feel demotivated, not to mention that the time you spent typing your rant into chat is time you didn't spend focusing on the actual match yourself.
5. Look at the map every so often
All warzones limit your line of sight in places, though some are worse at this than others. (Odessen is probably the worst at this, as in most places you can't see anything beyond the room you're currently in.) However, the locations of your team mates are always displayed on the map and can help you make decisions about where to best reinforce after a death or when to help with an attack. If you ever find yourself wondering "Where is everyone?", the map is your friend.
6. Keep an eye on your ops frames
I know it's not very intuitive if you don't play a healer (and I do in fact know some people who like to hide their ops frames altogether to improve their fps), but everyone benefits from having a look at their team's health bars every now and then. First off because the general state of people's health gives you an idea of how you're holding up against the enemy team (everyone being close to full most of the time is a sign that you're kicking ass, while people going from one hundred to zero percent health in seconds is a bad sign), but more importantly because it can help you make better decisions in combination with the advice given above: If the map shows you that Bob is guarding an objective on his own for example, and Bob's health suddenly starts dropping, you'll know that he's under attack and you can go help him out, whether he has the sense to call for help in chat or not.
7. Do the maths
I saw this explained in a lot of detail in a video once, but I don't remember where exactly. The gist of it is that especially in node-based game types, you should always keep in mind that both teams have eight players each (the occasional quitter notwithstanding) and move around the map accordingly. As an extreme example, if you see seven opponents run towards one of the turrets in Civil War, that means that at least one of the other two remaining turrets can't have an enemy nearby right now (as only one enemy player is left unaccounted for), and you might want to have a go at capping this potentially unguarded target.
More commonly you may notice that you're having an uneven fight somewhere (e.g. four vs. two), which means that numbers must be tilted the opposite way elsewhere. This is important because if a large number of your team is fighting a small number of enemies, it means you are leaving yourself exposed to a large-scale assault somewhere else (and you may want to move). Conversely, if a small number of you manage to keep a lot of enemies busy, you could reasonably expect the rest of your team to overwhelm their opponents elsewhere and hopefully turn the fight in your favour.