Do I really need a marking pencil or tailor chalk to do my markings for my sewing lines, or can I just use a #2 pencil? :?

if you're sure it will wash out use anything you like, I've never had trouble with pencil and often use them

Are they sewing lines that will show up later? I use a pencil or even a pen sometimes to mark the lines for my half-square triangles, but those marks will never show. If there is a chance of being seen, such as a quilting line or an actual sew-on line on the right side of the fabrics, you will want to make really really sure that the marks will come out.

are you marking the front or the back of the fabric?

I used a pencil years ago, and it did not wash out

I use pencil all the time and I never had a problem. Make sure to mark lightly. Also, after I wash the quilt, I check it closely to be sure the lines are gone. If they are not, I put some laundry detergent (liquid kind) directly on the places that still have marks and rub gently (like you would on regular laundry to get out stains). Then I rewash and check it again. The most I've ever had to wash was 3 times and that was because I marked too heavily. Once the marks are gone, toss it in the dryer.

The front

When I use pencil, I use a mechanical pencil with a very fine lead.

If it is a quide for quilting then yes you need something that will come out.

I use the Treasure Marker from www.cottagemills.com....look under notions. It's a "pencil" that you can use the black graphite or switch out and use the white soapstone. I've used it for a year, always washes out and haven't had to sharpen it yet! I LOVE this thing...in fact, I have one on order for a quilting friend!