Preferred seat is in the RF bleachers next to the aisle, no more than 3 or 4 rows from the exit. Easy access to beer, Hot Dougs, and a quick run down the stairs to the main level for the bathroom. Also have the benefit of a great view of the video board for replays. LF bleachers you are more likely to get a home run ball, but you have to turn all the way around to see the board.
I got to sit on the 3rd base-line right next to the bullpen home plate one time before the bullpens got moved. It was the game the Cubs clinched the playoff berth in 2016 on a Miggy oppo homer. I got to see the bullpen sessions of Kyle Hendricks (pre-game) and Aroldis Chapman (warmup) and they were both crazy awesome in their own ways. That was a great place to sit, but the big draw was being next to the bullpen for me.
I either take the red line or grab a cab and have them drop me off 3 or 4 blocks north of the field and walk down Sheffield. I like walking through the neighborhood on the way to the stadium.
Hot Dougs is usually the go to for me. My favorite was the Dick Tidrow. It was some sort of sausage with shredded smoked gouda, fried plantains, and a tasty gourmet mustard.
Pre and post game I prefer Murphy's. You usually see a former Cub or current Cub in there. I had a great chat with John Mallee one very drunken night.