Understand the basics of musical notation (see resources). You write music on a staff that consists of lines and spaces representing the notes in music. Sheet music also contains elements that let musicians know whether the music is in the treble or bass clef, what key the song is in, what time signature the song is in and in what rhythms the notes are played. It's important to gain an understanding of how to read music if you want to create sheet music.
Practice drawing some of the most-used music symbols and the various note rhythms. It takes a little time to be able to recreate musical notation neatly. Purchase blank sheet music paper from a local music store, or print it online free of charge (see resources). Use this paper to practice notating music before you attempt to notate a song. Some of the common symbols are clef signs (treble and bass), time signatures (which tell how many beats are played per bar of music) bar markings, and music notes.
Create a simple piece of sheet music to get a feel for how to format a music sheet. Draw the clef sign first. Make it treble since you want to keep it simple. Add a 4/4 time signature in front of the clef sign. This time signature is also known as common time because it is the most common time signature for music. It means you will have four beats per bar on your music sheet, made up of any combination of note values or their equal rest counterparts.
Write a whole note (held for the full four beats in 4/4 time) in the first bar. A whole note is an oval shape written on whichever line or space you want it to represent notewise. Draw a vertical black line to indicate the end of the first bar and the beginning of the second. Make the next bar four quarter notes (worth a single beat each) placed on a different line or space than your whole note, then end the bar and start a new one. Continue to do this until you have created a random musical pattern using eighth notes and sixteenth notes. You can repeat some of the same notes, but try to vary them as much as possible. The object here isn't so much to make a great musical composition, as it is to teach you how to format sheet music.
Add chord names over the top of each bar. Keep it simple at first. Use just one chord name, and make it match the name of the first note you use in your sheet music.
Try writing an actual song now. Compose on whatever instrument you use, and transfer what you play to your music sheet. Start with a simple song and finish it, then you can go back and add to it to create a more complex tune. The more you practice writing down the music you play, the better you will become at creating sheet music.
Consider choosing music notation software to alleviate the tediousness of hand notation. There are several music notation software products available for both PC and Mac (see resources). Finale is one of the leading programs of this type, available for PC and Mac.
Create a new document, which will resemble a traditional music sheet. With Finale, you can insert your musical note symbols from a menu or a toolbar. It's as simple as clicking the musical symbol you want, then clicking on the music staff where you want the symbol to appear. You can choose from an array of musical ornaments to indicate dynamics as well, including both often used and infrequently used symbols.
Score your music sheet and listen to it as you go. Most of the musical notation software today includes a playback feature that will play your composition to you in much the same way voice recognition software will read text.
Use the MIDI features of your computer in Finale (and most of the higher priced software) to play your music, and let the software take care of the notation for you. You'll need to ensure the sound card in your computer supports this feature by checking the sound card's documentation. If it does, you can hook a MIDI compatible keyboard to your computer, usually by USB, and notate your music by playing it normally and allowing Finale to transcribe it.
Print your music sheets using standard computer paper. Your notation software will print all of the elements of your sheet music, including the staff, onto standard paper, giving you professional quality music scores.