Just to tack on to the great advice that
@laurabeaumont provided, the sort of work you will be doing also depends on how busy your department is and what sort of work your supervisor is willing to let you do. But just to give you an example of the sort of work you might be doing (pulling from my own VS experience), you could be:
- Proofreading documents (incl. a contract);
- Preparing/delivering a presentation to your supervisor(s) (who will probably also invite others to come along);
- Drafting up emails for someone else (I did this once);
- Writing a research brief on something legal (eg, upcoming legislation) or commercial (eg, on green hydrogen); or
- Helping draft one of the firm's new articles (eg, this, though fear not, you probably will just be drafting a specific portion, not the whole thing)
Definitely knowing how to use Westlaw and LexisNexis is useful, but you should also know how to research stuff and find credible sources outside of those portals (eg, Google) – this is particularly relevant if you're doing non-legal tasks (like draft a research brief on how solar panels work).
Aside from keeping good notes of your process, which Laura suggested, also keep track of the work you've been assigned. In particular, you'd want to know right off the bat when you get a piece of work: what is the work; who assigned it; who its for; the context of the work (this is key for understanding the relevance of what you're doing – IMO, it also makes the work more interesting); how frequently you need to keep your assigner updated on your progress; when its due; what format and where you need to submit it in. I made a handy Excel spreadsheet for this. Keeping track of your process and the work you've done will most likely be handy for your final interview if you have one (eg, you might be asked how you deal with boring tasks). You might also be given access to the firm's intranet – if so, have a poke around if you've got spare time (and there's no work they can give you) and see more up close what the firm's all about.
At the end of the day, it's important to be proactive (ask for work if you have capacity) and be approachable (ask to meet people, and prepare some questions to ask but let the conversation flow naturally). As an example, during my VS, I asked a lawyer who previously worked in the firm's China office about his work there (contrasting to London) and we ended up talking in full Chinese about our favourite dishes and reminiscing about life in China. Not saying necessarily that every conversation you have must come to this point (most of my conversations didn't get to this point), but just don't overthink it and treat whomever you're speaking to as just another human being you're trying to learn more about – in any case, they're most likely very happy that you've expressed an interest in their work. Also try and figure stuff out on your own before turning for help, be the best version of yourself, and genuinely try and have fun while you're there.
Final tip: Message people who did the VS at the firm last cycle on LinkedIn and ask them what sort of work they did, and if they got a TC from it, ask them what tips they've got.
Best of luck on your VS!