Alternate cryptocurrencies are great, but please refine your ideas long enough and build a solid infrastructure. Don't be late on launch, have executables for all platforms + source code available, have a working block explorer, some currency exchanges (probably from YourCoin <-> USD / EUR), existing services (not necessarily anything big, but something for people to abuse their coins, poker for example) etc.

Have big enough starting difficulty so it will be more equal playground for everyone. Name your currency wisely. Encourage people to mine and test their services / setups on testnet, before launch to find any potential problems etc.