After a few hundred miles the bike should be checked over and the brake/shifter cables readjusted...they stretch a bit when brand new...spokes checked for proper tension and truing...they too can reseat and stretch a bit. All nuts and bolts checked for proper tightness.
After that, depending on how often you ride, I suggest cleaning and lubing your chain every month, wipe down wheel rims and tires with a mild cleaner...I use Windex lol...you also are looking at the tires for cuts, things that may be stuck in them, etc. Wipe down the frame and if you like give it a quick polish...I've used Endust/or another furniture polish, lightly sprayed on a clean cloth, auto spray instant shine, etc...
Depending on your skill you can remove the wheels from the bike and lightly sand, with a med...200ish or a tiny bit more coarse...grit sand paper to remove debris, then wipe then with the Windex to remove the material...brakes will grab nicely with the debris and glazing removed.
Check seat post binder bolt, stem/handlebars bolts for tightness every couple of months or so, especially for the first year of the bikes life.
I check tire air pressure every 4 to 5 days.
If you do this maintenance routine every month or two during the riding season your bike will ride like new all the time.

Once you develop a routine/rhythm it should take you approx. 30 to 45 minutes for the above. At least that is what it takes me.
Enjoy !!!