Or just do nothing.  It's not like you have to make your opinion heard on every post you happen to like.  But yeah, if you've got some sMerits, that's the way to go and the merit system is basically what this forum has for a "like" feature.

By the way, this topic of having/not having a "like" feature has been brought up numerous times before, and the community response to the suggestion has generally been negative.  For one thing, it's unnecessary because we have the merit system, and for another it could and most likely would be abused by members with grudges against people.  And personally I just think it's a stupid feature on a forum like this.  On Youtube it makes sense, because it lets content creators know how well their videos are being received (and on Reddit I don't think it's needed).  On bitcointalk it would be just a redundant feature since merits are used to "like" posts.