Why is my screen black?
"When I put my phone onto the scope, all I see is a black screen even thought the phone is aligned with the scope."
If you have multiple cameras on your phone, the phone uses clever software to combine the image from each camera, so you see black. You need to download a specialist camera app that allows you to select and use just one camera. Procamera or FilmicPro will do this.
Why does the brightness or focus on the screen keep changing?
Camera apps default to auto brightness and auto focus, which means they keep changing. If you're photographing or filming a subject that isn't moving, like a perched bird, lock the focus and exposure. A specialist camera app will do this more effectively than the native camera app that comes with your phone, as it gives you more control over the camera settings and usually has a more helpful interface.
I struggle to line up my phone with my scope, help?
You need a phonescoping adapter which locks the phone safely onto the eyepiece of the scope. This will vastly improve the quality of your phonescoping! See below for more info.
Which scope should I buy?
The better the optics and the better the light gathering the better for phonescoping. But having said that, you don't need a top of the line scope to get decent results. Modern scopes with wide angle eyepieces, work better than old school scopes that tended to have very narrow eyepieces. Note also that if you're having to buy a scope, are you sure that phonescoping is right for you? Phonescoping is great when you already have a phone and a scope and all you need to add is an adapter...
Which phone should I buy?
Most phones will work ok for phonescoping, but more modern phones tend to have better cameras. Some phones have multiple cameras and the ones with x2 telephoto lenses seem to work particularly well for phonescoping, as they remove the need to use digital zoom (throwing away quality) to remove vignetting (the black circle you see around the image). Every phone/adapter/scope combination is different, so you might want to try before you buy...
I've seen many people recommending Samsung phones over iPhone and vice versa, but none of these people seem to have done a side by side comparison. Check out the spec of a phone you're looking at using the detail on wikipedia. The size of the sensor (in MP or megapixels - the bigger the better) is one factor. The focal length (eg. f1.4 - the smaller the better) is another. Raw stats alone don't tell the whole story however - the quality of the glass, and many other hardware and software details (that aren't shared by the manufacturers) will have an impact. If you like Android phones, stick with Android. If you like iPhones, stick with them.
Which adapter should I buy?
Most universal phonescoping adapters are fiddly, cumbersome and disappointing. The Swarovski VPA is the one exception I've seen to this, and its the adapter I use. Phoneskope make adapters that fit specific scopes and phones and are pretty decent.
It's also possible to make a phonescoping adapter. Some people fix a cheap phone case to a spare eyecup. If you're really good at making things, this might work out well. If you're not, you might end with something clunky and end up dropping your phone on the ground. Buying a proper adapter is usually not a bad option!
The Phonescoping group on Facebook is a great place to ask for more information as there are lots of members who have used different adapters with different phones and scopes.
Where else can I get help?
Join the Phonescoping group on Facebook. I dislike Facebook in general, but this phonescoping group is very friendly, and a good place to share your photos and videos.
Birdforum has a number of relevant forums here. It's pretty quiet, but there are posts now and again.