Like any investment, don't put in more than you're willing to lose 100% of.

That said, there are three "good" approaches

1. Buy what you can afford during the ICO "auction" and get what you get.
   Benefits include being an "early adopter", growing the platform, participating in initial value. Drawbacks include potentially getting a worthless product, potentially owning over inflated coin.

2. Buy immediately after the ICO. Benefits include buying at a "known" price, getting a product that actually exists, still being an early adopter. Drawbacks include, value can always still decrease, the project could still "crash" losing all value.

3. Set a tolerance limit buy order after the issue to buy during the first "panic sale". There will be a panic sale, it's a crypto and market makers will make sure there's at least one panic sale. Risks and rewards are the same as 2, but you may buy in at an extreme low.