start with something small and private.
Private yes. Small, not really. Small things tend to look kinda crummy, as there isn't much detail you can put into them that won't blur a bit once it's healed. I'm not saying go for a sleeve for your first tattoo, I'm saying if you get a tiny little thing the size of a quarter, in 10 years it will look like a big multicolored mole and you'll wonder what you were thinking. Because tattoos are addictive, best to start with a well-placed not-so-small piece that has great meaning to you, and then you can build on it if you want. I got a crescent moon on one shoulder and a tree branch on another shoulder, then DH built it into a large night-time tree.
Tattoos DH sees people regret: Names of living people, sports or band logos, kanji, "tribal," stuff picked off a wall, tattoos they saw on someone else, gang tattoos, prison tattoos, tattoos that are associated with gangs/prisons even if the person who got it was never in a gang or in jail (teardrops, spiderwebs, etc.), and the sort of typical Rainbow Brite stuff--hearts, roses, unicorns, dolphins. Also many military tattoos are later regretted, sad to say--people get them before shipping out, go to war, come back wishing that their entire memory of combat could be surgically removed from their brains. Last thing they want is a reminder. 
Tattoos DH sees people love forever: Religious tattoos, memorial pieces, unique tattoos that mean something to the person's profession or hobbies, replicas of fine artwork (Van Gogh, etc.), well-organized sleeves, culturally significant pieces (e.g. Japanese art), original art from a VERY high-quality artist--the kind who charges $500/hour and is booked years in advance.