Research carefully, avoiding low value techs. My typical research for trade strategy is the Republic Slingshot path. Every tech along the way is valuable trade bait if you get there first.
Alphabet=>Writing=>Code of Laws=>Philosophy=>Republic is my path 90% of the time. If on a Pangaea, you might skip CoL and research Philosophy ASAP, taking Literature as a freebie. Literature is a high trade value tech rarely researched by the AI. After that, I usually research Currency, then if you are lucky you can use that to trade into the MA