There's some great advice here already. I just wanted to reiterate that at four she is still very young. Many children are simply not ready to recognise letters and numbers at that age. Try to keep things playful, and resist the temptation to 'teach' her.
Read, read read to her. Then read more. Choose books with repetition and rhyme, that she can learn 'by heart' and join in. Point out letters, words, sounds as you read, but don't slow down to make it a chore. Play games 'the first to see a letter O on each page" if she is receptive. If not, just read.
Soon she will know the book 'by heart'. She will use pictures and the context to work out what is coming next, probably before she uses phonics to work it out - which is a sign of an intelligent reader. If you read one book twenty or thirty times a day because she likes it, that's great (if a bit boring for you!)
Someone mentioned Letterland from the UK. It works well for many children, but the emphasis is on the characters who 'are' the letters, eg Hairy Hat Man, Wicked Water witch, etc. Many children, however, stick on the characters and can need a lot of help to make the connection that hairy hat man is in fact 'h' who says 'hhhhuh'.
When you make the sounds, be careful to think about what letters really say. Eg s says 'ssssssss' not 'suh' - soften the sound if in doubt.
I know a lot of people emphasis just teaching sounds wihtout the letter names. I think that most children can learn both side by side, as long as you are clear - the letter is 'called' 's' and it says 'ssss'. This clarity can avoid confusion later.
The problem with letter magnets etc is that they are usually capitals. Again, I work with both lower case and capitals, but tell children what they are and the purpose of capitals - they are used for names and to start sentences. But always write correctly - you can point out things like full stops (periods) etc, and capitals, just dont make a big thing of 'teaching' them.
sorry, now dd has to type you some w, o and 'b's, so I'll finish, hope this rushed answer is of some help!
Oh yes, Jolly Phonics from the UK is brilliant, and i think better than Letterland - it has phsyical actions to go with each letter and sound. I've seen a lot of success with it, and it's play based.