Nag screens are those pages you see in some indie games when you exit - they normally say something like -
“If you enjoyed playing the game - why not buy a copy?”
Where “buy a copy” is hyperlinked to the buy page.
Kev
eh, they never work on me, I just ctrl+alt+del if I’m seriously impatient.
but for the casual games market, who knows.
now, a nag screen before each level start - that would work on me.
A non interrupting nagger during actual gameplay might actually be best.
When you start the game you don’t want to be nagged, you want give the game a try! now!
Nagging during quiting the game is perhaps the most annoying, as you want to quit! now! No positive feeling = no pay
When you see a translucent message every now and then while playing, it wouldn’t really be annoying, yet still reminding the player
not to mention 1 frame subliminal messages 
Nag screens that interrupt the game have the opposite effect on me. “No, I haven’t been enjoying the game because of all these popups, but thanks for asking”.
Every time a non-paying user in wurm checks how long he’s played (seems to be fairly common), he gets a “You haven’t paid yet!” reminder. 
Non-intrusive, yet guilt-inducing!
It depends. If they are unskipable they are just plain annoying. If they are just “nag nag buy me” they are just plain stupid.
Think of it as a way to promote the benefits of the full version. Tell and show em what they would get. My favorite nag screens are the one from marble blast and the one from intensity xs (which is more like a nagging sequence, showing various action packed short scenes of the later levels).
I think that a well crafted nagging screen can make quite the difference. Its like advertising, but its pretty much the only time where most of the audience is actually interested in the product.
So, if they want information, give it to em. If they arent interested or undecided, let em skip… otherwise you might turn those undecided people off.
edit: oh and yea… if its unskipable you’ll even turn those people off who were interested in reading that stuff once or twice.
The goal is to:
- get people “addicted” to the game
- once addicted, ask for the money! people are more likely to pay if they are into the game.
I don’t think a nag screen gets people addicted. You don’t want to tell players right from the start that there is money involved - let them play and then “hit” them with the nag/payment screen … ;D
oh god, I hate it when I think I’m playing the real thing, then get hit with a “haha, this wasn’t the real thing, give me money”
that’s not what I meant. I mean you let them play the real thing and then later you ask them to pay/support your game - after all, you spent a lot of time working on the game and if it’s an online game, you spend money on hosting etc. there’s nothing wrong with asking for money (all the big companies do) - I just don’t think the nag screen works - people are put off before they actually start to like the game.
Ah, ok.
I’m personally a big fan of the shareware idea.
Play the first third of the game for free. If you like it, pay for the full thing.
Best I’ve ever seen? Inaccessible gameplay areas that you can see and almost but not quite reach, and are revealed as requiring a powerup that is avaialble in the registered version :).
e.g. in isometric platformer, a cliff that you clearly are meant to jump up, but can’t quite manage, and a picture of a powerup on the wall of hte cliff, where the powerup is either introduced in the start-a-level or end-a-level screen as being reg-only, or in the image of the powerup it says [full version only]
Thanks for the useful comments
I’ve decided to go with an inoffensive nag screen which shows a couple of the pay to play levels. It appears only after you’ve played the game 5 times so shouldn’t effect those who just want to try it out and arn’t keen from the start.
Kev
So FWIW…
i have payed for shareware in the past because of nag screens.
IMO the most effective are oens that slow me down once per run, during start up, and make me stare at them for something longer then 5 seconds and less then 30.