Besides everything mentioned above are the 14 daily Hiawathas. They often have a converted F40 "cabbage"/NPCU on the south (railroad east) end, which somewhat gives you a chance to see Amtrak still running F40s. On a good day you can come very close to catching a 7/8 meet (around 14:50) and a 337/338 meet (around 15:50) at Deerfield. Likewise, all of the midday Metra trains are scheduled to meet hourly at Deerfield at x:26. Once the evening rush hour starts, about every other outbound Metra train turns short at the "West Deerfield" crossovers (MP 24.5, between the Hazel and Greenwood grade crossings, and paralleled by Chestnut Ave. on the west and Park Ave. on the east). The trains continue until just north of Greenwood Ave. and wait there while the engineer switches ends, conducts a brake test, and calls the CP dispatcher (AAR channel 44) in Minnesota for permission to go east. This can also provide the rare chance to hear Amtrak and Metra horns in this usually whistle-ban territory since they often will sound the horns when passing the train stopped on the mainline.
You can see some of the Milwaukee North line locales in
my photos. Many of those photos and videos are taken from the Deerfield station, while others are at Glenview, North Glenview, and at MP 25.5 (1.5 miles north of Deerfield station) where the mainline parallels Waukegan Road.
One other popular spot is Rondout, where Metra diverges on the single track Fox Lake sub and the CP C&M (Chicago and Milwaukee) sub continues north (railroad west) toward Milwaukee. (There is no longer a passenger station at Rondout, however, so it would not be accessible if you are depending on Metra for transportation.) There is still a manned tower at Rondout, and a pedestrian/bicycle bridge crosses the mainline where the North Shore Mundelein branch once ran. I have heard varoius things about how welcome railfans are at Rondout.
You might consider using a "stopover" if you are riding on to Fox Lake later. You can tell the conductor as you get your ticket punched that you are stopping over at an intermediate station and he/she will punch it appropriately. (A zone A to zone J ticket costs less than, e.g. an A-E ticket plus an E-J ticket.) You'll want to double-check whether a stopover requires you to ride the next train or allows you to linger for more than an hour.
Finally, one other possibility you could consider is that on weekdays, it is possible to connect between the North Central (Antioch) trains and the Milwaukee North (Fox Lake) trains at the adjacent Prairie Crossing stations serving both lines. CN (former WC) freights run on the Antioch line. You could, for example, depart Union Station and go to Prairie Crossing, then ride Milwaukee North back to one of the mainline stations.