Some sites has upload/download ratios - you could only download so much many files without uploading files, forcing an exchange rate.
There was a selection of download protocols you'd choose from, based on what your client support and the BBS supported: "KERMIT", "XMODEM", "YMODEM", "ZMODEM", and "JMODEM"
The better protocols supported batch, multi-file, compression, and resuming interrupted downloads - very important for when your session was interrupted by someone else in the house picking up the phone and trying to dial.
We had a second phone line installed for the modem; I learned how telephone wiring worked and re-wired the our phone outlets to use the correct lines.