DESERT CACTI AND OTHER SUCCULENTS:
The Desert cacti and most of the succulents love to receive as much sunshine as possible, and an ideal location for them would be a south facing position, where they can receive the most sunshine.
If a south facing position cannot be provided then a west or east facing window is the next best position, north facing windows should be avoided for growing cacti and succulents as they need sunshine to form their spines and flowers, if you only have a north facing window then cacti and succulents can only be grown if you can grow them outside during the Spring and Summer months where they can get plenty of sunshine during their main growing period and therefore overwintering them on a north window or location would not be a problem, however if you cannot do this then you can provide additional lighting by the form of LED growlights or other special growlamps that are made for growing plants.
If you only have a window that never gets any or not a lot of sunshine then you could install a special growlight for plants, LED growlights are very popular with indoor plant growers at the moment and as they offer a full spectrum of light they are ideal for bringing the sunshine into a sunless room and because LED growlights are often very affordable and inexpensive to both purchase and to run on electricity, they are ideal for adding extra light to your plants.
Here is a video below that I have made for my You Tube channel on the LED growlights that I like to use in our plant room:
If growing your cacti and succulents on a windowsill remember to turn your plants around every couple of weeks to avoid then growing towards the window and ending up resembling a leaning tower of Pisa haha!
Epiphytic cacti prefer to have a much shadier spot than the Desert types, and will tend to go yellow or red in a south facing position, and grow much more lush and green when grown in a more shadier spot such as a east or west facing position, where they can receive early morning or late afternoon sunshine. Epiphytic cacti can be grown in a south facing position if growing in the shade of other taller plants therefore blocking out some of the strong midday sunshine. Some growers have had good success with growing Epiphytic cacti in north facing windows, however in my experience I have found that they never flower for me if I keep them in a north position, but remember this is only my experience if you have had success growing these plants in a north facing position then please continue to do so and remember you can always add a LED growlight or two to encourage blooming in a north facing window.