Well, Let's say you've %100 premined 1 mil coin. I would distribute this coin like that;
10% of this coin: IPO
10% of this coin: ICO (x2 price of ip price)
10% of this coin: signature campaign
10% of this coin: twitter/fb shares, followers etc.
10% of this coin: 7 day mining
...
Something like that: which covers all of the methods to distribute coins. For instance: I want to mine then I'll mine it pow mining. I don't power to mine so I'll join sig campaign. I don't want to do anything bu want coins then I'll buy with ipo/ico etc.
Everyone can collect coins how they like.
What are differences between IPO and ICO?
PS: We can't use mining, there is no infrastructure for that, all the coins must be distributed before the genesis block.
Well, basic difference is price.
On ipo: you designate a time let's say it's a week.
You collect funds for a week, let's say it's around 12 BTC for 100k coins.
What's ipo price? 0.00012 btc for each coin.
On ico; you designate the price of the coin. You can say ICO price is 0.00024 btc for 100k coins. Then you can collect 24 BTC for it.
Basically prices are different.