Visiting neighbours

The single best thing to do is to find the buildings with the slowest recharge times that have a payout ready and select those. This usually results in a faster recharge for the neighbor and has no ill effect on you. The previous person replying mentioned some examples.

Near the bottom of the list is doing graffiti. It has the potential ill effects of lowering both your Righteousness rating and that of your neighbor's, at least until they clean it up. So you are lowering your bonus for both yourself and your neighbor, potentially outweighing the cash gained in such an action.

I usually avoid doing graffiti even if it means not doing 3 actions on that visit for those reasons.

In order for someone to benefit from your tapping a house or building, two things must happen:
1) The person must log in before the timer that you started runs out (please correct me if I’m wrong, but I don’t think the person will get any benefit if they accept the handshake after that timer has expired).
2) After accepting the handshake, the person must return soon after the “adjusted” timer runs out to tap the house again… because if they don’t, the shortened timer didn’t really help them.

For example, if I tap a friend’s pink house at 7pm, it’ll be ready again at 1am. The friend might log in at 9pm and accept the handshake (getting the same payout they would have if I didn’t tap it), but assuming they’ll be asleep, it didn’t matter that I bumped up the next renewal time from 3am up to 1am. They still won’t tap it again till morning, so it didn’t help them at all. However, if I instead were to tap a purple house at 7pm, there’s a chance that they’ll be able to log in and tap it before 10pm to accept the handshake, and again after 10pm to benefit from the earlier purple payout.

Therefore, the strategy that is most likely to benefit your friend is to tap houses or buildings that have the longest duration such that it still results in the timer running out before your friend goes to bed. Or, find ones with a timer that expires around the time you think your friend will wake up (for "stranger" friends, I just assume they're somewhere around Central timezone). Also the 24h and 48h timers are always a good choice. Here's a helpful list of some of the longer interval buildings, put together by tsotips.com:
2 days: Burns Manor; Krabappel’s Apartment
24 hours: Duff Stadium; Pimento Grove; Springfield Penitentiary; Springfield General Hospital; Volcano Lair; Holiday Tree; Santa’s Village
16 hours: Fat Tony’s Compound – Phineas Q. Butterfat’s; Springfield Library; Springfield Observatory; Orange House
12 hours: White House; Hibbert Family Practice; Sprawl-Mart; Santa’s Village; Sleep-Eazy Motel; Mapple Store; Wiggum House; First Church of Springfield; Skip’s Diner; School Bus
10 hours: Asia de Cuba; Legitimate Businessman’s Club; Howard’s Flowers; Springfield Cemetery; Springfield Pet Cemetery
8 hours: Swanky Fish; Springfield Coliseum; El Chemistri; King Toot’s; Jake’s Unisex Hair Salon; Sir Putt-a-lot’s; Springfield Buddhist Temple; Blue House; Aztec Theater; House of Evil; Mausoleum; Super Collider

funny but I had noticed sometimes during the day if I tapped on a handshake a few minutes later I could tap on the building again. Guess there is more to this game than is on the surface.