Which expansions or stuff packs are needed?
For my lots, you will need all expansions that I have unless stated otherwise. Unlike for Sims 1, it does not matter whether I've used items from a certain EP or not. With each EP installation, the game changes how lots are saved, which is why you need the same EPs I used. I do have AnyGameStarter by Numenor, so I may make lots requiring less EPs, although usually these are requests. At this time I have the following expansions: University, Nightlife, Open For Business, Pets, Seasons, Bon Voyage, Free Time, & Apartment Life.
You'll only need the stuff pack if I use items from the pack in the lot. I am told the stuff pack items with just disappear from the lot if you do not have that particular stuff pack. I currently have Family Fun Stuff, Glamour Life Stuff, Happy Holiday Stuff, Celebration Stuff, H&M Stuff, Teen Style Stuff, Kitchen and Bath Stuff, and Ikea Stuff.
For object recolors, it depends on the requirements for the original mesh. For Maxis recolors, I will base it on how they have placed objects in collections to determine this. If it is a custom mesh, I will rely on what the original mesh creator says is required.
Do I need to download a mesh somewhere?
When at all possible, I will include include the custom mesh when the creator's terms allow it. When I can't I will clearly state what mesh is needed and the creator's site. The same will be true of what you may have to download for a house.
I use WinRAR to archive (aka compress) what I share. If it is a ZIP archive, you will need a program to open it such as, WinZip, WinRAR, or 7zip to open it. If it is a RAR archive, you will need WinRAR, 7zip or another archiving program that supports multiple formats (WinZIP will not open RAR files).
Ok, so I downloaded it. What now?
All package files go into your My Documents/EA Games/The Sims 2/Downloads folder. If you have Nightlife or later, I highly recommend you subfolder your downloads in some way to make things easier on you. If a file is a Sims2Pack, you must double-click on the file to install the lot and any included custom content. You may also use Clean Installer to select which custom content pieces to install.