Thread by @uk_domain_names

Factors to decide which pro-Remain party (LibDems, Greens, Change UK, SNP, Plaid Cymru, Sinn Fein, Alliance, SDLP) to vote for...
- Detailed regional polling data
- Direction of travel in recent polls (who's rising, who's falling)
- Incumbent MEPs
- "Celebrity" candidates

Of course, the detailed regional polling data (where available) provides a decent first-cut look at where to deploy tactical votes to maximum effect. But you can also look out for trends (e.g. Change UK has gone down in recent polls)

Also, you might expect an incumbent MEP to get a (small amount) more traction and name recognition than the polls might suggest, especially if they've been doing a lot of local campaign. And of course well known names can't hurt (e.g. Gavin Esler)

Another consideration: what's happening to the Labour vote. That's going to be by far the richest territory for pro-Remain vote stealing as word gets around that Labour aren't a pro-Remain party. So that could change things up a bit as we get close to election day.

Finally, a couple of extra wildcards (as if trying to read the tea leaves wasn't hard enough)...
- Turnout and voter behaviour (will supporters of some parties prove more willing to come out and vote than of others?)
- Weather (what happens if it's sunny or if chucking it down?)

Have I missed anything obvious? There's other stuff like scandals, bold PR moves etc. but that seems to cover the main factors I think.