My own basics;
1) Remember the debate is public, not personal.
You are rarely going to change an ideologues mind. But you can equip others on your side with good arguments and resources, and maybe sway people who would otherwise be persuaded by them. Argue with a goal to putting forwards a case against them, not necessarily changing their mind or 'winning'.
2) Try to use debates to learn something.
Even if I can't change other people's minds I can better understand my own beliefs, dig up new and better resources and maybe learn a few completely new things. If I haven't looked at a certain topic for a while then spending a bit time constructing arguments about it is a good way to revise and refresh.
3) Focus on the strongest arguments your opposition
could put forwards and the root of their beliefs.
A lot of people online will use trivial or just plain crap arguments and make it easy to score points by slapping them down. That's kinda fun at first, but means nothing in the grand scheme of things. Researching the opponents positions and understanding the reasons they are making the arguments then focusing on those is a lot more effective.
4) Ignore insults and personal attacks completely.
This is just a personal choice, mostly to do with point 1. Let your opposition dig their own grave. In the past I've even cut insults out of quoted posts as though they didn't happen which amusingly resulted in them calling me out for editing their quotes. At the same time I tend to feel more free to call out insults directed at other people, especially if thrown by people supposedly on my side in the debate.
The same goes for completely incoherent arguments or those where they are just stating the same things over and over, ignoring your rebuttals. If you find you are just repeating yourself over and over again without any progress, feel free to walk away and let your posts stand on their own.
5) Ideas have inertia. Public opinions doubly so.
People don't change their mind overnight, especially if they have expressed a view. Backing down is hard to do and people tend to prefer to save face. Never expect someone to reverse their position even if you have destroyed their arguments. That said, even if they refuse to give any ground, just making them aware of the opposition arguments (especially arguments they can't counter or dismiss easily) is a good way to plant a seed of doubt and change that, given time, can help their views to shift. I've know people online who have eventually changed their minds on topics from creationism to global warming to the existence of god. They were vitriolic and passionate in their original positions, refusing to consider any contrary points, but walked away from the debates for months or years and came back with their views completely reversed.
6) Read lots, post little.
Yeah, good joke given my walls of text. But I try not to enter a subject unless I've got a good handle on both the topic - reading likely arguments both sides are going to use - and the current climate of the thread in question.
7) There are no win conditions.
There are no lose conditions either. You decide what is a positive debate and what is a negative debate. Try to work out goals related to the other points and, if you don't feel you are accomplishing anything, walk away.
8) Calling out fallacies is no substitute for an actual argument.
Just calling something a strawman or ad homin isn't going to mean anything to someone who finds the illogical argument convincing. Try to be a bit more detailed if at all possible. Or at least provide more detailed rebuttals and explanations for why the fallacies are bad arguments that shouldn't be given the weight they are. And even then don't expect that to have any power in convincing the other side of your view.
And just wanted to touch on this;
1. Arguments should be impersonal. This is about ideas, not people.
This falls into the civility and tone argument problem. A lot of topics are directly personal for some. A lot of arguments that are dispassionate and academic for one side are direct attacks on the person of the other.
I've seen people make dispassionate arguments that a certain type of person
doesn't deserve to live who then dismiss people who fit into that category because they got angry and emotional.
That's before noting that the best writing for actually convincing people is emotional. Ignoring that and trying to pretend we are all beings of pure logic is to ignore the way the world works. I've also notice a lot of people who don't recognise that their own arguments are based on emotional responses but are willing to call out other people's as such when they need to dismiss them.