Plenty of Facebook groups that publicise these marches well in advance. I think there's one planned in Inverness in a few weeks' time, which I'll maybe go to.
Marches and all that are well enough, but what they need is real get-out-the-vote initiatives, ahead of all the regular elections, and particularly ahead of the next Referendum.
And there will be a next Referendum; personally, I think they should hold off a wee while yet, until the full weight of the Brexit catastrophe has hit.
It's apparent from last time that there's a chunk of people who simply won't take a risk and vote on the hope of something better, unless they take a look around and genuinely reckon things can't get worse.
A no-deal Brexit, and a few more years with the Tories (Red or Blue) in charge ought to take care of that.