Lukewarm is between warm and normal temperature. Ex: the bath water was lukewarm. So lukewarm actions would be a soft action between a hard or bold action and doing nothing at all. An example could be your reaction to a noisy person in a movie theatre: Hard action: confronting the person No reaction: ignore the noisy person Lukewarm: shhhhh! :)

I agree with Wes but "lukewarm actions" sounds a bit unusual to me in this usage. I would probably say something like "half measures" to convey this meaning instead. For example: Half measures do not work. We must take full action instead. We don't take any half measures. Usually when we use the word lukewarm in a figurative sense it would be to convey an unenthusiastic response to something. For example: The latest film was met with a lukewarm response.

Adding to Wes's answer. A lukewarm reulst is similarly something that does not provide a good result, but some result. The term is used to mean "not very effective". . Hoping that this gets a better than lukewrm reception.