If your child is at the initial stage of learning to write for the first time, it's not really important to worry about lines at all.  Just have them practice letters anywhere on the page.  If you're past that stage then have them try to write the letters on a line (and in a line).  Make sure the line spacing is big since they are still learning the fine motor skills necessary to make the letters.  You can use a page with lots of lines if you want.  There's no specific number.

The steps I follow (which seem consistent with a variety of early penmanship programs): 1 - preschool: writing letters "freestyle" (no lines).  2 - early kindergarten: writing letters in a line, on a line (just the baseline). 3 -  mid-kindergarten: writing letters using 3 lines: baseline, topline, midline (usually dotted), 4 - late first grade: writing letters using 2 lines: baseline and topline. Letters also get smaller (lines closer together) at each step, as children refine their technique.  Hope this helps!

It would be wise to check with the school your child is enrolled in to see what their protocol is.  Handwriting programs vary greatly.  For example Handwriting Without Tears uses only two lines while Zaner Bloser uses two solid lines and a middle dotted line.  It is important to be consistent with your child's school to keep confusion to a minimum.  It makes learning easier if everyone is on the same page so to speak.

We have better motor memory in our larger rotational joints and muscles.  Practice the shapes or letters very large in the beginning.  After a child learns the motor movements large, move them to paper.  Its alot easier!

It really does not matter. You should try different approaches... customize fonts, sizes, enmbed pictures.... They need contextual support in the beginning. Later on you can eliminate some help, but basically use different approachers.  We are using in my school fonts for teachers (www.fonts4teachers.com ... if i am not mistaken) and it is working really well.
Dana Uribe
Principal, LAUSD - CA

I don't think you have to worry about how many lines they are writing on, until they begin instruction in school. Let them write their letters anywhere they want, on the paper.

Another fun way to have your child practice writing, is to write in a thin layer of something on a tray or plate.  Try things like chocolate syrup or jelly - if the letters are formed correctly they get to lick their fingers!  Rice, corn, salt, flour or sugar on a baking sheet can work well, just gently shake it out to erase it ready for the next letters.  Another kid favorite is shaving cream (non menthol), which doubles as a cleaner for the table surface.  These suggestions work well for young children just learning to write, or for lower grades who need to practice writing spelling words. I teach preschool kiddos, and I like to match the medium to the letters we're working on: write Ss in sand or salt, Ff in flour, Pp in peanut butter, etc.

no lines,,is the best..then slowly introduce the 3 lines