It's very easy, you have several ways to see if a stock is diluting, for example, if you see an ask of 20k shares, for example, and, 200k shares are traded on the ask, or more trades, and the ask stays the same, this means the stock is diluting.
Also, if trades are done at the ask, and the ask drops, this is a signal of dilution.
T-trades are also signal of dilution.
When the bid jumps and has a big order, and, it is fulfilled almost immediately.