Did the developers of the various premined coins have to wait for those coins to be mined first or did they change the code to first issue themselves the premined coins?
I'm referring to the list of coins at http://altcoins.com/scamcoins
There are various ways to premine coins, some are use for scam coins and others are used by experimental altcoins.
The premining made by scam coins are usually made with 3 methods:
1-At the first method the guy create the coin and start to mine it, after some amount of time he tell the internet the coin exist and promote it. At this moment he already have alot of coins. After it, he sell the coins he has to the public.
2-The second method involves the guy promoting the coin, but just creating a thread about the coin at some forum and not really advertising it, he just start to really advertise the coin after he has already mined alot of coins. The difference between this and number one is that this method will reduce the amount of people that will say the coin is a scam. After people start to mine the coins, he can see the coins to those who want.
3-The third involves selling all the coins to the public, everyone pay some amount of money and each person that gave money to the project get some % of the coins based at the amount of money they paid to the developers. After they receive the money, they gradually stop to work at the coin. Mining is made to get transaction fees.
Then there are the other premine method, used by experimental coins, some say some (or all) of those ideas are bad ones, but they aren't made by people trying really scam others, but by people that want to try the idea or think they can work.
1-The previous idea 3 can be used in a non scam coin. If that's the case, the developers will really continue to work at the coin, after they receive the money.
2-Another method include burning coins. People sent another altcoin (at some implementations a specific coin, at others various coins can be burned) to a place that will then (at the moment they sent the coins or at a specific date) burn their coins. The users that burned the coins will receive money from the new coin based at the amount of coins they burned. They can either receive X coins for every Y coins their burned, or Z% of the total amount of coins based at the % of total burned coins that came from him.
3-Other method includes, sharing the coin equally between everyone that ask. When the coin "start to run" everyone will have their own coin.
4-This fourth method involves people mining the coin as usual, but the coin is blocked, you can't use the coin until all coins are mined.
5-At the fifth method, people don't mine coins, but they mine numbers. People use their computers to mine numbers and after some amount of months or years the mining stop. After the mining stop, all coins are spread between the users, based at the amount of numbers they mined, if there are 100 coins and 3 users mined numbers, the first one mining 30 numbers, the second mining 50 numbers and the third 120. The first guy will get 15 coins, the second one will get 25 coins and the third one. will get 60 coins.
At method 3 of of scam premine and all the 5 method of non scam premine you can either have transaction fees, where people mine those fees, or demurrage, where the system get X coins (or X% of your coins) every Y months and give back to the system to be mined.