We'll meet up and be split into groups. The groups (each will have someone experienced) will try to visit the legislators who have constituents in that group. During the meeting (with the legislator if you're very fortunate, often with a staffer/assistant), you point out items that are of interest to you, explain what support/vote you're requesting, and provide information to support your viewpoint.
That's pretty much it, in 100 words or less. If you go on the VCDL lobby day, you will be with others who have done this before. I encourage you to give it a try. I never have before, but will certainly be there this time.