I use the typical wire minnow basket with cone funnels on each end. I take 30lb mono and run 2 strands crosswise forming an X where the 2 halves meet. take white bread, knead it until if forms an air free dough ball, then press the doughball onto the mono X... that suspends the dough in the middle of the trap so the minnows have to swim in to get to the bait. Tie a 15 ft string to a coke bottle float and set trap near bait. That system will catch 100 minnows at a time if put in a good area.
Cast nets are great for saltwater, I carry on on my boat in case I come across a large pod of bait. That being said, I prefer fishing artificials and not fooling with live bait, so don't do it often.... BUT for freshwater, you are going to need much smaller mesh openings (prob 1/4 in) than saltwater, as you are looking for smaller bait than what I'm looking for fishing saltwater