When singing, most guitarists are playing rhythm. Not always but most often. Unless you're playing a unison, it's hard to play a lead and sing something else at the same time.

I simply started by playing along to records and play the guitar while singing.

Regarding the words..... yeah.... you have to remember the words. What will happen as you do this more is that you will have your head in the song with the lyrics and your playing will be on automatic. You will not be thinking about the chords on the guitar. That will be coming from a subconscious level.

You have to sing with confidence. No one wants to hear a singer who sounds like that are afraid to sing. When you walk on stage and there's a packed house, sing like you own the place and the PA isn't working and you need that guy in the back to hear you. Don't strain your voice.... just don't hold it back unnaturally. Regarding mics and volume.... first off... you should forget about the audience. They don't exist. Get into the song.... listen to your voice and treat it like an instrument. If the song needs a soft passage, that's what you do. BUT... you don't sing soft thinking the mic and amplifiers are going to make up the difference. Sing the song the way it should be sung.

Another issue is singing by yourself, you will often hold back. Don't do that. Sing like there's a sold out arena waiting to hear you sing..... let it all out.

Holding back makes your voice weak and you will not be able to stay on pitch. Sing with strength and confidence.

Hope this helps.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.