Here are some tips for the newer players.
- Always make sure your walls are high enough to block grenades and make sure that they have a curve at the top for maximum defence
- A good entrace is a monitored entrace. Have a tunnel inside your wall, but have it guarded by another player, who will shoot hostiles that try to get through. The entrace will be hidden so that only people on the same team will know where it is. The entrace will be moved at the end of each combat phase.
- At least two layers of walls is always a good defensive strategy. Also make sure you have Firing Holes for your team meates to easily fire outwards from. This will make it harder for enemies to survive the trip to your base.
- Put your flag inside some kind of tower or to make it harder for hostiles to get to it and try to protect Friendly Spawn Points with makeshift bunkers
- Always make sure you have Good Short Range Attackers and at least one Engineer at your base at all times. By doing that, your base will be harder to get into, and the Engineers can continue construction in the event you don't suceed to finish your fort before the build phase ends. The Engineers are also very useful when it comes to repairs.
This guide is also available if you want to make sure your base is as easy to defend as possible:
http://www.sourcefortsmod.com/index.php?p=site_userguide_bases