Getting 1 new Public Works Project suggestion every day isn't hard. Sometimes it can take a long time. But be patient, because it WILL happen. The first suggestion of the day is always there for the taking if you spend enough time to get it. Sometimes it'll come to you without even trying, while other times you'll need to slog through a ton of boring villager babble.
But if you follow these steps, you'll get at least one suggestion a day.
Step 1: Imprisonment
Bust out your shovel and dig holes around every villager walking around town. If you're looking for a specific PWP suggestion and the villager you need to get it from isn't walking around, Save & Quit until they pop up. But imprison everybody, regardless. They deserve it. You know what they did.
Make sure you catch them all. Patrol the entire area. There can be as many as 5, or as few as 2 (really late/early in the morning).
Step 2: Encumbrance
Get rid of any fish, bugs, or furniture you're carrying. Next, fill your entire inventory with flowers or bell bags. This is something a lot of people do wrong when they do the diving trick; they empty their inventory rather than fill it up. If you have open spots in your inventory, villagers can offer to sell things to you or give you gifts. You don't want all that donk. Fill up on things they won't want to buy. Bells are probably the most convenient way to go.
Step 3: Inertia
This is the "diving" part of the "diving trick." You don't necessary need to dive. You just need to pass time away from your prisoners. This USUALLY results in resetting their dialogue. BUT, I still recommend diving. I find it to be more consistent, as often I've idled elsewhere and gotten no reactions from anyone even after spending enough time away from everyone.
Put on your wetsuit and go for a swim. Just leave your character there to feed the jellyfish while you go on the internet and look at funny cat videos or whatever. If you don't like being stung by jellyfish there's a spot by the dock where they can't get you. Sissy.
Step 4: Discovery
Go walk in front of all your villagers. Don't talk to them, just walk in front of their faces.
One (and only one) of them will have a surprised reaction and try to run to you (but can't, because you've imprisoned them like a responsible overlord should). Talk to them and see what they want. Most of the time it'll be something stupid, like "What flower best represents me/you?" or "My greeting's getting stale" or some sort of emotional insecurity crisis like "Am I stylish?"
If you're lucky, one of them will give you a PWP suggestion. Good. Now you're done. Free your prisoners (or don't) and get on with your life. If not, then...
Step 5: Repeat
Repeat.
Every Hour: Nagging
Every hour or so, your villagers will want to nag you about playing too long. When this happens, NO ONE will try to run up to you until you talk to somebody and get nagged to take a break. Don't take a break. EVER.
This can be used to your advantage if you're trying for a specific PWP suggestion. DON'T run in front of the villager who could potentially give the PWP you want. Instead, avoid them entirely, and talk to another one for your nagging. Then, go walk in front of the villager you want a PWP from. The FIRST villager you walk in front of (who hasn't seen you in a while), after getting the nag message, will ALWAYS be the one with a surprised reaction.
Advanced: Getting a Specific Suggestion
Certain projects only come from certain personality types. See here:
http://animalcrossing.wikia.com/wiki/Public_Works_Projects
You can go after a specific personality type's suggestion by simply not talking to anybody but him/her. If another villager type has a surprised reaction, just ignore them. You still should trigger the surprised reaction, just to ensure it'll be reset after your next dive/idling.
Doing this, I got all my Snooty and Smug suggestions long before the others. I still have dozens of suggestions to get from all the other types. But I specifically wanted a Statue Fountain, Sphinx, Pyramid, Moai Statue, and Stone Henge, so I went after those first.
If you don't get the suggestion you want, you can reset without saving and try for another. But it's best to just move on. A bad suggestion just means they have one less thing they can suggest to you, so there's a higher chance of getting what you want next time.
How long should this take?
That depends. If you don't care what villager type you get a suggestion from, it shouldn't take long. Sometimes I get it in 5 minutes. Sometimes an hour. But as long as it's your 1st PWP suggestion of the day, it won't take very long. Just be sure you're paying attention to the time and checking all of your villagers for reactions every 3-6 minutes.
If you're after a specific PWP suggestion it can sometimes take a couple hours. Reason is, you're skipping potential suggestions from other types in order to get one from the personality type you want.
Bonus round: More suggestions?
I don't recommend doing this, because it's VERY rare and not really worth the time. But it's possible to get more than one suggestion in a day. I've gotten 2 in a day once, and I've seen several people mention getting 3. But it's totally random, and really rare. Getting 1 is guaranteed. I've never failed to get 1 as long as I kept following these steps. But every time I try for 2, it never happens. It only happened that one time when I wasn't even trying!
If you wanna blow a bunch of time trying for 2, go ahead. But you're honestly better off just waiting for the next day for a new one.
---
And that's that. PWP suggestions are a rare and random thing if you just play normally, but 1 can be forced every day if you use this method.
