First and foremost let me tell you that what these ICO are offering is trust less contracts, that in itself is a big problem and actually makes no sense, you are investing for an idea and most of the time that wont work, keeping aside that, if you find a good project that attracts you, you need to read carefully their white paper and make an assessment whether it is feasible as they say and if you think that has a good theoretical purpose, then you can invest in it, another thing is that, even thought the white paper is attractive they might not fulfill what they set out to be, over all it is a big gamble.