Some tips for seed investor wanna be

Had a startup, love to help people and now having needed connections and resources I would like to support startups in my country financially by making some seed investments. Unfortunately on the Internet there are almost no materials about startup financing and securing your interests from the seed investor point of view. I would like to start a discussion about this unpopular ;-) topic. My main concern is securing my right and profits in the startups. I would like to partly cash-out on some investments after several months without waiting 3-5 years. One way to secure my interests is to insist to generate new shares in a startup for following investors by share splitting. This way I can secure my % share for some time but the fact is that probably most founders will not accept that way. The standard thing is issuing new shares with existing shareholders dilution. But in that situation where is my theoretical earning at each stage after my seed investment (early investments, round A, etc) when despite company valuation going up my % share going proportionally down? The standard thing is issuing new shares with dilution of