By transcribing do you mean simply figuring out music by ear? Or also formally notating what you hear in sheet music?
From my experience this is what works for me:
– Listen to whatever you want to figure out SEVERAL times. Listen to the song more times than you think you need to. You need to keep listening until you can play back the entire piece in your head from memory.
– When you listen, really listen to the piece. Meaning you’re not on the internet or your phone or doing anything else. All you’re doing is focusing and listening. On this note, I often find it helpful to close my eyes when I listen.
– Also try to focus your ear just on the particular instrument that you want to transcribe. For example, if you want to figure out a rhythm guitar part then you’re only listening to the rhythm guitar, you’re not paying attention to the drums, bass or vocals. The ability to focus your ear on a particular instrument at a time is a skill that you develop with practice.
– When you listen, also listen for the particular nuances of how he’s playing. For example, say you’re transcribing a solo. Is the note bent? Picked? Legato? Does he slide up to? Slide down? Also listen carefully to the vibrato. Is it wide? Narrow? Fast? Slow? etc You want to listen for all these subtleties. Again this is a skill that you get better at with time. Same goes for figuring out rhythm parts. Is it palm muted? Barre chords or open chords? What’s the picking pattern of the arpeggio? etc
– After you’ve done this much listening THEN it’s time to grab your guitar and start figuring it out. At this point, it becomes a process of refinement where you figure pieces at a time and then “check your work” so to speak by listening to the recording again and comparing to what you have. So say you start by just trying to figure out the intro riff, you don’t worry about the rest of the song yet..
– Take breaks when transcribing. Your ears get burnt out and you get mentally burnt out. You will often find that you “revise” your transcription because it isn’t quite right at first but after taking a break and coming to it you figure out the right way to play it. Listen at quiet volumes so you can listen for longer without your ears getting burnt out. Also accept that it may take you longer than you want to learn something but you will figure it out with patience and hard work.
Learning to play music by ear can be a difficult process but the more you practice it the better you will get and it will pay HUGE rewards to your tone, playing and writing ability.
As for recommended songs, I would say figure out anything that you like. Personally I started by figuring out synth parts in pop music because I liked that and they were simple. But lots of classic rock, early metal and punk would work well too. Commercials are great sources of ear training too.
Pretty much any software that can slow down music works. There are different ones out there on the market go try some demoes and see what you like.
As for questions on theory and ear training, learning some theory can help you figure out what notes are likely candidates and transcribing is a form of ear training. Just a more advanced one.
I hope that helped.