- Look for a follower with "the uniform" (Tango shoes, knee length dress)
Appearance-wise, I wouldn't ask (cabeceo,
walkeceo, etc.) if they're wearing something that might inconvenience me (e.g. from personal experience: dress covered in glitter - spent ten minutes in the gents scraping it off my sleeve; back of dress covered in rhinestones - made for a very pokey tanda).
Shoes: heels do generally (but not always) indicate that they want to follow; for ladies in flats, I tend not to look at them unless I've seen them following. If they still have their boots/street shoes on, obviously not.
Otherwise, I don't really care much about what they're wearing.
- What is the greatest distance you'll try cabeceo?
Probably some tables away (not a very exact measurement!), depending on the lighting conditions, as long as I can see her eyes clearly. If need be, I'll walk closer, but never too close (since that would just make her uncomfortable).
- Do you do a "walkeceo" or change seats each tanda to strive for spatial diversity?
Yes, but I only start walking once the tanda has begun. If I know what the next tanda is, I'll strategically position myself (standing or sitting) to be in direct line of sight of the follower/s I want to dance with.
As for strategies, they really vary - I tend to keep to myself, but here and there I'll strike up a conversation with people at the refreshments area, bar, coatroom, etc.. I've had a few tandas that way since it's a nice and unobtrusive way to draw followers' attention and make myself be more than just a nameless face in the crowd. They might also introduce you to other people.
I've had followers verbally ask me to dance in the middle of a conversation, and I've also asked them in similar situations. Something like
Oh! this is a very nice Di Sarli tanda, would you like to dance it? It does need quite a bit of delicacy and tact to sense if they're willing to dance though. If you're not wanting to ask directly, maybe a comment or two about how good the music is in order to hint at wanting to dance before resuming the conversation. At times, it's not even needed - your eyes might meet, you might tilt your head or raise an eyebrow or nod towards the floor, and it's off to the races.
Like TTanguero said, be seen dancing.
Most of the above applies for ladies from your area, I suppose - if you can keep track of them (or if they tell you) throughout the event.
It also really depends on the layout of the event venue. I've been to a few (pre-Covid) where it was just a massive free-for-all, with people crowding around and trying to get onto the dance floor before the live band started playing - in such a chaotic situation, I'd just try my best to catch someone's eye.