Serial Romantic

Start with making a lot of friends first and building up charisma, that will make flirting easier. Then once friends, invite sims over and flirt them, go on dates, etc.....I tend to have most of dates at my sims home unless I want drama, as there is less of a chance of my sims getting caught by another love interest and will just take longer since your sim will be embarrassed and the other angry. I am fine with taking longer and all that personally for storytelling; but sticking to dates at home is the quickest and least painful way. Sims can still come over and see your sim with another; but if you don't give them a house key, you should be alright.

I don't do this aspiration for every sim; but it what worked the best for me when I do use that aspiration.