Liberalism depends on the competition, and what exactly you need. A few of my ideas on Liberlaism
MOST IMPORTANT! Do not lose the game trying to get there first. It is a beeline, so much is sacrificed, usually guilds (knights) and Engineering (pikes/trebs). Make sure an AI is not going to slam you with Superior Mideival stuff.
Now
How to get there:
1) The big techs are Philosophy, Paper, Education. Most AIs are slow teching these although some of the wonder hogs (Pericles, Mansa, Darius, Liz) will also bveeline and bulb them. All can be bulbed with a GS
2) Understand "What can be let go". You can get ALOT of good backfill techs off Philosphy if you get there first. Education is almost always worth selling for Guilds, Engineering, and other fillins to 2 AIs. However, make sure you are close to teching off Liberalism.
3) My general preference is to manually tech Paper which is fairly cheap for it's time, Bulb most of education (2 GSs for it is a waste), and Philosphy varies. The AI will usually NOT tech education early.
4) I generally will tech liberalism right away to get one of several favored techs (more on that in a bit) ASAP which helps you out early. Sure you can save it (sometimes even the post-scientific Method techs) but why wait so long to get a distinct tech advantage.
5) Liberalism is much more than a free tech. It opens two of the strongest research Civics in teh game, Free Speech (Very big for a CE based game) and FR (helps tech rate, happiness, and sometime invaluable for diplomacy). Thus the faster you get it, the faster you will overall tech.
Now, What to take for free???????? Depends on numerous things including the competition, empire status, map, victory path.
So here are the one I generally get, in the usual preference
Nationalism: Really depends alot if I need to war very soon or whether an AI manually researched it. Benefits are first crack at the Taj and a free GA (which if you play your cards right can lead to string of others by getting 3 more GPs, usually 1 for free from economics). The Taj GA also allows you to wait to adjust civics without Anarchy, especially if you are industrious and/or have Marble. The other benefit of Nationalsim first is the Draft. Getting an edge to draft Muskets and rifles before teh AI can is a big advantage, especially for survival or planning to take out a tough customer (and a supreme back-stabbing tech).
Astronomy: If you are isolated (a lone continent even if you MET everyone via optics), or already conquered you continent. Oversea trade routes get's you ALOT of commerce as well as opens up resource trading which can eliminate alot of happiness/unhealthiness problems. Also you have a new beeline, gunpowder/engineering/chemistry for some serious naval supremacy in Galleons/Frigates/Privateers.
Printing Press: Less popular only because the next GS can usually bulb most of it. However, taking Printing Press and swapping to Free Speech is a MAJOR uplift to the CE game! It also opens up the path to rifling (guilds/banking/replaceable part/rifling).
Economics: A weaker tech but a Free Merchant is nothing to sneeze, nor is early Free Market! If you can trade for nationhood and eventually Consitution, you have quick access to coproration for another trade route, thus doubling those trade routes in sometimes 2 techs.
Chemistry: Trading off eduation pre-liberalism can typically get me Guilds/Banking/Gunpowder/Engineering if I have several stupid, I mean friendly partners. Nab Chemistry, tech Military Science and upgrade you CR II and CR III maces to grenaders and finish teh game, or at least the continent.
Those are techs I can always get at Monarch, and usually at Emperor. Now you may be able to nab things like Scientific Method, Democracy, even Steel but if you getting those for free, you basically DON'T need the free tech to win
