Peggy, I'd be delighted to share my thoughts about early writing. It's a subject that fascinates me. I'll describe what happens if a child is not taught to write in a formal way, but helped to develop naturally.
The most important thing is that a child needs to be allowed to continue to believe that he or she can write, even though what they write doesn't look exactly the same as what an adult would write. Sadly, this self belief is often lost when children are instructed too rigidly and not allowed to experiment with print in a developmental way. But I need to be clear that I do not believe that a child should just be 'left to develop' without help - it is the adult's role to facilitate and lead the learning on to the next stage, and to reinforce what has already been learned.
The earliest stage in developmental writing is scribble -once the child has learned how to make marks on paper. The next stage is generally 'reading' their scribble aloud. After scribble and marks on paper generally comes some attempt at symbols, eg rows of o's or dashes or a familiar letter, such as the first letter of the child's name. These symbols willl gradually become more accurately representative of letters, often two or three that are repeated over and over. And gradually the left to right direction and clear lines of print will evolve.
Eventually the letters will begin to be bunched together as 'words'. In time, the first letter of some words will begin to be accurate, especially in a child who learns phonics easily. Most children can identify the first letter of words before the end letter, and the middle letters come last (usually the vowels are the final stage)
Gradually the words become more accurate, and punctuation begins to be used. A whole word learner will often use correct whole words in his or her print rather than follow a phonetic pattern. Often this type of learner will stick to familiar words in his writing as he gradually builds up a written vocabulary, so his writing may be repetitive.
The adult role is to show interest, and give feedback. Feedback should be specific and personalised, not just 'good job' at every attempt, which does not lead to further learning. But of course, the role is not to 'correct' either!
A useful phrase to use is "Oh, you have written cat 'c-a-o-p'. Shall I show you how I write cat?" Then the child can decide if he wants you to give help and show him, or not. Some children will ask you to spell out words for them before trying to write them themselves. I discourage this, but try to do it in partnership - "What do you think cat will start with?" If you spell out every word yourself you end up with a passive partner, not an active learner.
Have lots of writing materials available and do activities such as making little books, reading them back, writing for real purposes, (eg recipes, thank you notes, shopping lists etc). As your child does a drawing, ask if he wants to write about it, or for you to do it if he dictates. Suggest making it into a poster or a card.
If you scribe as he dictates, talk about what you are doing. This is called pole bridging, ie: talking your thoughts aloud. Encourage your child to do the same thing. Adding verbal language to learning reinforces what is being processed.
Most importantly, treat your child like she is already a writer - she is! show interest in what she writes and pay careful attention to what she already knows about print and what you can help her to understand next. Don't underestimate what she can do, point out punctuation to her as you write - not in a formal 'lesson' way, but conversationally, just as you would point out something interesting in a book or as you are out doing errands. She won't fully understand yet, but it will draw her attention. Use correct terminology, 'letter' 'word' 'sentence' etc.
Use fantasy for writing, eg in her play house give her pads of paper to write notes, play post office, or secretaries, or even school! Take what she writes seriously and ask her to read it to you. Point out what she could do to make her writing clearer, "I leave spaces between my words so that they are easier to see, can you do that?"
Obviously, you know your child and know the pace to take things. There will be times when you just read what she has written and use it, don't make every experience an opportunity for instruction. Children vary, some are so aware that their writing is not 'correct' that they ask for input at each stage, others would be put off by too much input so you need to take it slower. Trust your instinct and your knowledge of your child to tell you what pace to set.
I hope that this helps. This is a very quick guide to early writing, there is much more to tell, I will elaborate if you like. You can do some more formal activities too if your child wants to do them - word building and sentence building, but with a young child I tend to take a more developmental approach unless the child asks for more 'instruction'.
And by the way, I use 'he' and 'she' interchangeably, it's habit!