How to accept and detect altcoin payments?
Most (99%) altcoins are just Bitcoin clones, so the same process applies, you just need to use the appropriate daemon (dogecoind, litecoind, etc). If you need extra help, we'd need to know which altcoin. In addition depending on how popular the altcoin is there may be the equivalent of Blockchain.info (has merchant services for Bitcoin), eg. DogeAPI.