There is an excellent guide for first time users of DC++ at http://www.b.ali.btinternet.co.uk/DCPlusPlus/gettingStarted.html. The guide below gives instructions on setting up your internet connection and DC++ client to connect best to other users. Or there is the FAQ on this wiki.
Early versions of DC often have security issues or problems downloading and mods of DC++ are often very unstable. As such, all clients older than v0.674 are banned, and a version greater than or equal to 0.699 is recommended. For full details on which client you require and for details on clients for other operating systems please see the How to Connect page.
Instructions for setting up your client to download
Please note that if you have successfully connected to the hub (can chat and see the user list), then ALL searching and downloading problems due to either your client/computer not being set up correctly OR the person you are trying to download off being on the other side of the University firewall. To see a list of users who are on campus, type -resnet into the main hub window. If you think you have done all of this but still cannot download then please see the Downloading Help checklist.
Downloading and Uploading - Speeds
When downloading a file, you will get the best speed if both you and the other party are on campus. Up to 11MB/sec can be achieved this way. Much slower speeds will be obtained if one or both parties are off campus. If you are after new episodes of things, it is generally advisable to torrent them, rather than waiting for a slot off people on twofo. Off campus people can only expect speeds of probably up to and around 30kb/s. This is due to the limitations on the upload speed of a standard broadband connection these days
Downloading and Uploading - What works
Because of the way IP addresses are allocated on the Campus Residential Network, transferring files to/from addresses outside this network will NOT work the majority of the time. So in order to download from somebody when you are on Resnet, the other person must also be on the Resnet. The library and University House along with all other parts of main campus do not count as Resnet and as such you cannot download from people on Resnet from these locations. Active mode is strongly recommended as this allows you to connect to the maximum number of people. If you are in Passive mode then you are unable to download from anybody else in passive mode. This is typically around 10% of those on campus and 40% of those off campus. There are excellent guides to setting up your client to use active mode successfully on the Help page of this wiki
Why is passive mode so bad?
In passive mode, DC++ will only make outbound connections to other users. All searches will be sent through the hub, and search results will be returned through the hub as well. DC++ will return a maximum of 5 search hits for a passive user. Passive users cannot download from other passive users. Passive mode is an extra strain on hubs, so please do not use it unless you must. DC++ users in passive mode will have M:P in their DC++ tag.
That being said, active mode on DC++ will make inbound and outbound connections to other users. All searches will be sent through the hub, and search results will be returned directly from active mode users and through the hub for the passive users. Active users can download from either active and passive users. Obviously, that means you can connect to a larger group of people.