If you do a search here at the gardenweb forums for "no till" or "lasagna bed" (include the quotes) you'll find just what you need...and pictures, too.

What 3 lines are marked? Are they gas, hydro and telephone?

If this is a newer home, and based on my local codes the lines should be 4 - 6 ft deep. THAT DOES NOT MEAN THEY ARE!

You can dig down with a shovel and see if you find the lines. Once you know they are more than say 15", stop digging - you can now safely till the ground for a garden.

Keep in mind that the marks are +/- 1 ft in accuracy, so you need to dig perpendicular to the lines making a 2 ft trench.

If the lines are less than 15" down - do not put a garden there, unless you raise the whole area 15" obove the lines and never dig deeper. I might even cover the lines with wood boards or metal rods so you can't dig deeper.

I put in new hydro lines and had to cross both gas and hydro lines. I dug down more than 2 feet and did not find the lines. However, I know that the telephone line near the house is about 4" deep.

That should answer your question. Now for some advice.

There is absolutely no reason to till the ground. This is true for a new garden as well as an existing one. Tilling only damages soil structure and brings up weeds. NEVER TILL THE GROUND. That is the old way of doing things wrong.

Lasagna method works well if you now have grass - search other posts for this - lots of entries. Or just add 6" of fresh top soil (not 'fill dirt') on top of what is there - making raised beds with lower walk ways. There is no need to edge the raised bed with wood, but it looks neater. Then plant.

If you mulch your vegtable beds you will never have to 'dig up the whole garden' or till it. Just harvest and plant. the less you disturb the soil the less weeds you will have.

This advice assumes you have some decent soil to start with.

thank you all for your advice...treelover i was stuck on a regular garden, i had seen the raised and lasagna bed and just moved on...but you made me stop and think...i posted here and on the vegetable garden forum...someone there posted a ton of pics on different gardens...and there was two that had areas made and then mulched around and they look fabulous, almost like a nice little pretty flower garden...which is great for a backyard vegetable garden in my opinion because you can make it fit into your surrounding landscaping...i am so glad i took the time and not be just set on the one idea. Madtripper the lines are ELECTRIC...thats the one that scares me, telephone, and cable. My dad says those lines have a trip on them that if you hit them they shut off...not that he was encouraging digging there was just saying in general conversation, i don't want to be the one to find out and i know they are supposed to be deep but i don't trust that much energy going through one single source let alone someone possibly in a hurry placing lines...just scares me- i dont want curly hair lol. Thanks to both of you for such great advice!