I plan by generating a list of candidates and then view on an opportunistic basis during the evening. GoTo certainly streamlines things - there's a penalty in setup time but less frustration (IMHO) for the remainder of the evening. Seeing, light pollution, haze, cloud etc. are potential obstacles, but I work around those as they occur. As for a backup, I simply move on to the next object on the list.
There are resources online that can help - my favourite is
Tonight's Sky, which will generate a viewing list for you based on parameters you enter.
Tonight's Sky is fairly easy to use, e.g. select:
(1) Lat/Long
(2) Horizon obstruction
(3) Timezone, viewing start time and duration
(4) Difficulty (e.g. select everything up to and including "easy" at 8.5 mag)
(5) Object type(s)
... then click the big red button to generate your viewing list.
You can further sort or edit the list before printing it out.
Having a play with Stellarium can also help orient you to what's visible on the night you will be viewing.