What is an altcoin?

Blockchain technology was invented by Satoshi Nakamoto, the creator of Bitcoin. Every coin, that also uses blockchain technology has more or less the same base logic with some additional features. They were all created after Bitcoin as an alternative, thats why we call them altcoins. There are some other "coins" in creation, that use a little different base (for example IOTA, which has the "tangle" instead of the "blockchain"), but they are still called altcoins, because they are still an alternative. Some altcoins are just a pure clone of other coins and offer no invention - except another name. Though they often get pumped, they have very less chance to succeed. 

Kidding me with "become rich"?

No, this is no joke. Blockchain technology can really make you rich. We experience the beginning of a new era. This is comparable to the computer and internet technology before the dot com bubble and the altcoins are a new form of open source stocks.

Just look: Yahoo went up nearly 100 fold in about 5 years (it fell afterwards, but it still was up about 10 times then). Amazon went up 100 fold in about 20 years. Microsoft went up 100 fold in 10 years. Apple started in a garage and is now the most valuable company in the world!

But this is NOTHING against blockchain. You know why? All those stock companies had an IPO at the beginning. None of those companies started with less then 1 billion market cap, when they hit the stock market. So they were already relatively expensive at the beginning. 

Crypto coins start with several millions market cap. One Bitcoin rose from less than a dollar to now over 660$ in 7.5 years and it's still cheap with 10 billion market cap. Ether market cap rose from 21 million to more than a billion in 1 year! NXT started with less then 100 bitcoin investment and was worth more than 100 million. NEM was partially even free and up to a maximum of 0.2 BTC per stake (2,250,000 XEM) at the beginning, wich is worth now roughly 150 times after 2 years, and it's still only 70 million market cap! The list is endless.
This is an really incredible opportunity!

How much should I invest?

Of course this depends on ones liquidity but the golden rule is: "Don't invest, what you need for living!"

Read it again, just to make sure, you follow it strictly! Write it down and hang it in your room. You can't be a long term investor, if you need the money. That just doesn't work. You - may - be a short term investor, if you are good in trading back and forth, but I also wouldn't recommend that (it's not good for the nerves as well).

The money, you invest, shouldn't ideally hurt you at all. If an altcoin was broken completely and your investment down to nothing, you should be able to just shrug shoulders and buy another one. So choose wisely, how much you can afford to loose in order to still have something to invest.

It doesn't matter if you can spare only 10 bucks for one coin, if 10 bucks is a lot for you, because if the coin goes tenfold you'll still be glad and maybe you can use the profit for spending more next time. But you really have to make sure, that you don't need the money...

Which altcoins should I choose?

This is the toughest question. I really can't tell you. Here you have to do your own research. Read, read and read. Don't ask, because people will mostly tell you only those coins, they are trying to sell...

Read all kind of news about blockchain. Build up your knowledge, so that you learn to decide.
Keep track on the coin market caps. Sign up at bitcointalk.org and stay up to date with the altcoin announcements as well as the altcoin discussion. Further I suggest to regularly read the news on cointelegraph.com and coindesk.com. You also may want to know about the newest ICOs.

In the end you have to decide it on your own, but I can give you some hints, to make it a little easier.

Try to invest in many coins at the same time

If you invested in just one company in 1995, the chance would be very high, that it was a company, that messed up. The company may have been good at that time, but made a bad mistake and your money would be gone now. If you choose only one company, it's just luck, to choose the right one. But if you choose your "top 30" of the most promising coins, you have a good chance, that you chose the 1995 apple, microsoft and yahoo as well.

Only invest in really new ideas

Is it really an invention, or just a clone? STEEM was a good example for a completely new idea. Also NXT was a good example. It was the first coin, that had an asset exchange for a decentralized trading. It went down a lot, but now they may have a renaissance with Ardor (more or less a NXT 2.0). Ethereum made the smart contracts presentable. All those examples would have been a excellent choice when they came out. God knows, if they still are :-)

Research the developers

It's important, that they are accepted in the community. Read posts in their threads. Look if there is anything fishy. The best thing is, if they already developed another (more or less) successful coin. For example Lisk was programmed by the guys of Crypti which made it somehow trustful, but of course you still can't know, how it turns out to be.

How good is the marketing?

Marketing is one of the most important things for new coins. Even Dogecoin as a clone of bitcoin could reach kind of high (2013) with their memes. There are already more than 650 coins out there and the market is getting narrower right now. It's harder for new coins to assert and that's why their appearance should be "shiny". Make sure, they have a nice logo. Their website should have style. You should feel comfortable with it. The coin and you will have a long time together after all ;-)

When should I sell?

This is also a difficult question. I will only answer you this question as a long term investor. I don't like the pump and dump short term things. You may make money with it as well, but for me it is more like a casino visit with maybe a little better odds. I tried it a little and I was not really lucky. Now I only invest in things I believe in, that's why I don't sell them easily.

You may want to read a little more about ROI, but the advices are mostly for short term investments. With apple for example the best thing would have been to just keep it.

I suggest to keep all until it grows at least about 5-10 times. Then I would cash out 10-20%, so that you have your investment back, wich you can invest in something else. The rest I would keep until another 5-10 times, before I would cash out some more, because then it's really worth it. But I would never sell all. You will bite your ass, if it goes through the roof :-)

And now I wish you good luck with your investments!