I have been harvesting for years and if you keep it low key, no one is ever going to notice. For poker, find somewhere that spreads limit, and buy-in for 3-4 racks of $1s. Then while you are playing, sort out the best chips. Then whenever you are ready, leave the table and pocket all the good chips as you walk to the cage to cash out the bad chips. Easy to get over a rack this way every time depending on condition. If you have to play no limit the advice above on how to accumulate the $1 chips is perfect.
Lately though, I have been harvesting playing Craps using the "Dead Man's Hedge" play extension strategy. You can harvest 20-30 chips an hour with ease and your expected loss will be well below $5/hour. Just pocket a 3-6 chips when a seven out happens and the dealers are busy clearing the table. When a dealer shift happens pocket as many as you want. Just keep changing out $5s for $1s as you get low on $1s which is normal and will not be questioned. While not many casinos spread poker, most spread Craps, so you can get just about any chips you want that way and they will likely be in better condition than poker chips.
Blackjack works well if you can find a $1 or $3 table. You can do it at $5/$10/$15 tables by changing out $5s for $1s and betting odd amounts that will accumulate $1s. Pocket 3-6 chips when the dealer is shuffling, or as many as you want on dealer changes.
Lot's of harvesters are more aggressive and work the cage or get the dealers or other players involved, but that's never been my style. The casinos generally are not going to care unless you are grabbing fractional chips which they would to lose money on. It's pure profit for them if you harvest anything above a $1 chip. I have never been caught or questioned, and have harvested 10s of thousands of Paulsons.