I always use the same routine when my sims have dates. Maybe it's not the best way but it use to work for me and always seems to result in a dream date.

I dress the playable sim in formal wear and let him/her use the phone to ask for a date. First stop is always a restaurant there I try to use as many of the date interactions as possible (hold hands, do a toast and so). The date becomes a better grade if the playable sim pays. After the dinner I always send the couple of to a place to dance. After some "good" interactions (hugging and kissing etc, this can be done many tims though the date) I let the sim ask for some slow music and let the couple do the slowdance. Whit all the avalible interactions. After some time I have them stop and do some more hug, kiss interactions. I also let the playable sim ask the partner about his/hers fears and wants. And give away a gift if there is any avalible.

I'm no love doctor here but this use to work for me.