Configuring a game is not that hard. Intuition alone should be sufficient in understanding all the ruleset files. Grab the ruleset files from github and have a look around - it should all make sense after a couple of minutes. If you're having any troubles, the IRC channels #freeciv or #longturn on irc.freenode.net will help you. The freeciv wiki might be outdated, or describe a different version of the game, so don't rely on it too much.
Once you've made a ruleset with your favourite settings it's time to make it known: make a thread about it in this forum. If the changes aren't too radical this will be a ranking LT game. If the rules are controversial or experimental, and a significant number of players would want to play it (say, 10), then a non-ranking game will be created.
If everything looks fine I'll take it from here - create the game on the WWW and create a subforum, handle the signups, run the game server etc.
If you have some good ideas but don't want to edit the ruleset then define them clearly and post them anyway, and I'll try and make the ruleset changes. This is what happened in LT33 where wieder had some good ideas.
Don't hesitate to contact me with any questions either here, on irc, jabber or thru email.
Grab the ruleset files from github and have a look around
I was planning on doing that, but I can't find anything there except a pretty extensive list of updates and a bunch of READMEs. Any directions, please?
Download the ruleset and install it on your local computer.
Then start making changes. Something simple first. Like changing the cost of a warrior. Try changing the cost for example. Change it from 10 to 5 and test that.
You do that by opening the file units.ruleset and editing this part of it with some text editor. Notepad will do fine but don't use Word.
name = _("Warriors")
class = "Land"
tech_req = "None"
obsolete_by = "Pikemen"
graphic = "u.warriors"
graphic_alt = "-"
sound_move = "m_warriors"
sound_move_alt = "m_generic"
sound_fight = "f_warriors"
sound_fight_alt = "f_generic"
build_cost = 10
pop_cost = 0
attack = 1
defense = 1
hitpoints = 10
firepower = 1
move_rate = 3
vision_radius_sq = 18
transport_cap = 0
fuel = 0
uk_happy = 1
uk_shield = 1
uk_food = 0
uk_gold = 0
flags = ""
roles = "DefendOk", "FirstBuild"
helptext = _("\
This unit may be built from the start of the game. It is the\
weakest offensive unit.\
First make a rough list about the goals you have for the ruleset. Like making it easier to build a strong economy or fight early wars. While it's relatively easy to edit most parts, it's much harder to end up with a balanced game. LT33 is a great example of this. We still don't know if it was balanced enough or not. It's looking good but there is need for making some of the wonders expire later or make them cheaper. This is because of the fast pace of the game and this is partly because lots of people know how to play the game.
What kind of design goals do you have?