**I just got my MIL’s sewing machine, so it’s time.**FYI–the sewing machine might have to be serviced/overhauled, especially if it’s been stored a long time. If it’s a good machine, then it’s worth it. What kind is it? How old?
**I though I would start with a table cloth, seems simple.**Nope. Your questions demonstrate why a tablecloth isn’t so simple. It’s hard to get it exactly straight and exactly right so that it hangs nicely. And it’s a heck of a lot of fabric to waste if you mess it up.
Try something smaller, first. Like the napkins to go with the tablecloth. Drawstring bags are easy and fun, and you don’t have to get them just right. I just made a bunch of cedar sachets to store with my woollens. I had some pretty fabric, and I just made simple bags and filled them with aromatic cedar shavings from the pet store. They’re kind of cockeyed, but who cares?
**1) If my table is 45 inches wide and most fabric is 45 inches wide (what does 44/45" mean?) that means I need to have a seam down the middle to get any tablecloth hanging over the edges, right?**You’ll probably want to find some extra-wide fabric when you make the tablecloth. Seams in tablecloths usually are bad.
**2)how do you press that 1/4 hem in? Is it “measure…press…measure…press” and so on. It seems really tedious, am I missing some trick?**Sounds like you’re missing some basic techniques and a few good sewing notions. I’d suggest getting a book about basic sewing. Your library and bookstore should have lots of them.
**3)If the cut edge of the fabric isn’t exactly straight, how do I get my hem exactly straight?**You have to cut the fabric straight yourself. But first you have to make sure that the grain of the fabric is straight so it all stays straight. Yeah. Sorry. That doesn’t help much, does it. Get a book with pictures.
**4)any really really obvious things about sewing someone clueless enough to ask the preceeding questions might need to be told?**Lots of things! Get a book with lots of handy tips and tricks. And I’m sure we Dopers will supply some good tips. (maybe you’d get a good response about general sewing tips in IMHO)
Here’s a tip from me: Use good thread. Use only good thread. Regular Coats & Clark from the discount store is the pits. It’s weak and it fuzzes. I use Mettler or Gutermann. My preference is for the 100% cotton “silk finish” from Mettler. If I want more strength, I use Metrosene from Mettler.