Trust me, its far too easy to sound smart in trading and yet you can't make a dollar yourself. I could name names on here, but I won't bother.
The very best proof is a real time call of your trade with entry price. I don't even care if you don't have a stop or target in mind yet. But at least now, anyone can look at the time stamp of the post and look on a chart to see if it makes sense.
I also like charts with the trades marked by the platform, but this can of course be faked, so if the results are too good, one has to question.
Lastly, a screenshot of trade fills from broker or platform is also good, cause I can plot them myself on a chart, but this can also be faked, but at least its a start.