If you have a look at the links in my signature, you'll get a couple of starting points to look at. There is also the
pine64.pro site which I couldn't in fit due to the signature length limit.
There isn't a quick start or instruction guide for the pine64 yet... this board is no-where near the newbie friendly nature of the Raspberry Pi just yet, but the information base is starting to come together.
With respect to keyboard - you should be able to use any old USB keyboard. Just please DON'T use your fancy $120 keyboard (if you have one), as someone found to his dismay that it self-destructed, although that appeared to be a fault on the keyboards part... but it's just not worth it!
Audio... depending on which software package you use, you might need to configure things a bit, but you should be able to plug anything that normally goes into a 3.5mm headphones socket... i.e. computer speakers, headphones, etc.
Display-wise... since the connector is HDMI, a TV or monitor that has a compatible connector should work. There has been some commentary as to certain devices not working properly, but your mileage my vary... you never know until you try.
You may find it handy to have several microSD cards depending on what you intend to use the pine64 for, and how much you want to experiment with it. Since changing operating systems can be as easy as powering down the system and exchanging microSD cards, it's handy to have a couple so you can experiment with different things.
You may also fine it useful to have a USB to Serial adaptor handy, as that helps with troubleshooting, and also gives you another way to control the pine64 without a keyboard or display. The only think that you need to be aware of here is that it must be 3.3v compatiable, otherwise it will damage the pine64. I usually recommend something like
this one (
with some jumper wires), or you could go with
something like this if you want something a little more ready to use
Until we get a better idea as to what your use case is for the board, and how familiar with linux and single board computers like this, it's a bit hard to go into any further detail. You'll find lots of bits and pieces of the forum, and don't be afraid to ask questions if you get stuck with anything. The IRC chat is also a good place to drop by if you want some more immediate one-on-one contact.