1st rule of Fight Back Club - Absolutely no infighting or weakness in public
This is what the right do well. During what could've been a messy protracted tory leadership bloodbath was resolved when Andrea Leadsom stepped-down to pave the way for unelected May. A deal was probably done, something they're good at - partly because their participants can be incentivised and placated by money and status. The left need to know when to do deals behind closed doors.
So when Owen Jones or The Guardian or a Labour MP says something you disagree with or is engaged in arguments with their own side calmly tell them to stop public squabbling. Share this article instead.
Use simple catchy slogans and repeat them relentlessly - see Bernie Sanders' populist rhetoric
"It was the banks!" - use colloquial phrases like tax dodgers, fat cats, big business. The tin-pot tories at UKIP have tried to co-opt this and the left have let it happen.
"Fighting for justice are not liberal values, they are human values"
Stop getting distracted by frivolous news - see 'dead cat'
This plays into the psychological phenomenon called Parkinson's law of triviality or "bike-shedding"
On the flip-side, look for political capital in the most frivolous distracting news, especially as this content is more likely goes viral and reach casually-political audiences.
A bit of research and discipline turns the huge Oscar wrong best picture story into an attack on reckless incompetent corporate culture:
@JeSuisFedUp @TheMarkRomano to be clear it was PWC, a financial service co. that screwed up. The type of folks Trump is stacking govt with.— SFBCA Fishing Club (@SFBCAfishing) 27 February 2017
Stop advancing the careers of professional trolls
Do create or post memes that tell a simple story effectively. People aren't swayed by facts - they are swayed by stories and pictures help. If anyone tells you memes are silly then it's because they have no counter-argument to the actual content - so point this out, call them weak and trying to play the distraction game. They hate that.
Calmly and consistently undermine any opponent by using their own work against them. Remind everyone of these repeatedly whatever the context. Always be ready to screenshots their tweets to save to your armoury.