Just the usual warmup rules. And carry a spare warm battery in a pocket if you're dependent on those. It's hard to predict the weather in Feb. It might be relatively warm with lots of wildflowers and almond orchards already blooming down below, or there cold be cold rain and even snow in the Valley, often on the soggy side that time of year. Yosemite Valley itself isn't very high, but can become a cold sink for the air higher up where snow will still be quite heavy. And it can be especially cold in the shade. March is often cooler than Feb, but the weather is so screwed-up these days, i'd just prepare for anything mildly wacky.

If you have a spare day or two in the area, don't count out the Mother Lode hill country down below. Yosemite Valley itself is just the tip of the iceberg, photographically. Of course, the high country itself won't be accessible except to hard-core backcountry skiers, although you can get a bit of a distant view up at Glacier Point if that road is open.

Size of tripod? - all depends on if you need to ram the feet down into snow or not. It's a headache to use a lightweight CF tripod in snow or a spongy meadow; but I've done it thousands of times when the travel priority was lighter wt gear. Bring warm waterproof boots, not just hiking shoes. There aren't many safe pedestrian turnout spots on the paved roads themselves. But trails should be relatively uncrowded that early in the season.