Help learning how to hem

I am just learning to sew.  My grandmother was an awesome seamstress but she passed before she taught me much about it and so I am trying to learn on my own and I do alright but I am having alot of trouble with hems and wondered if y'all can give me any tips to make it easier for me?  I recently made a poodle skirt for my daughter and the hem was the hardest thing to do on the whole thing.  I also have been making those pillowcase dresses for her (not out of pillowcases though) and I just never can get that part right.  It always ends up looking terrible   Thank y'all very much!
Mary

Welcome to sewing!
Hems can be tough. They are tedious and frustrating especially round hems such as the one on your poodle skirt. These are some of the hardest to accomplish neatly. This is why for most circle skirts/dresses, the hem is a rolled one which is done on a serger. Some sewing machines have a rolled hem foot which can make life easier once you master how to use it. If you do not have a serger or the special foot, my suggestion for these types of hems is to make it a very small or narrow hem. I have learned that narrow hems are easier to accomplish on these types of garments.
And as for other hems, practice is the best advice. Get yourself a hemming ruler and use it. These are usually very cheap and easy to find. My favorite ones are the gauges with a sliding marker for easy repeated measuring like this Dritz one: http://www.amazon.com/Dritz-Sewing-Gauge/dp/B0001DSJMC.
Many people try to eye-ball it and I really don't think that's a good idea if you are new to sewing. Keep at it and you'll be a hemming pro before you know it!

For circle skirts, if you're working with a fabric that's synthetic, you can use this product called Steam-a-Seam 2.  It's a fusible double-sided tape.  You press the non-papered side to the wrong side edge of the bottom, take the tape off, fold over and press again so that the fusible fuses to the fabric.  This stuff gives you a nice, crisp fold.  If I'm using a woven, I'll fold over again and topstitch...if I'm using a knit, I'll just topstitch it after I've fused it.

The curvier the hem, the harder it's going to be to hem it.  Keeping the hem allowance super narrow (Steam-A-Seam is 1/4" in width for instance) will help keep the hem from bunching up and creating weird little gathers that are not so pretty. 

If you want to make a deeper, curvier hem (say 2" or something), you can make little wedge-shaped cuts no deeper than 1" from the fold at evenly spaced intervals.  Handstitch the cut edges together.  This will help eliminate the excess fabric that makes for those icky nasty gathers in your hem and help you press a nice, clean hem.

If this feels overwhelming, start with simpler hems that are straight or more straight like an A-line skirt or even something as simple as napkins.  Honestly just hemming up a bunch of fabric scraps for practice will give you more experience and make the garment hems not so scary.  You can do it!

I'll throw in that you can make yourself a set of pressing templates from cardstock or manila folders that will make fast work of pressing hems.

Cut varying widths of cardstock--1/4", 1/2", 5/8", 3/4", 1", 1 1/4" etc.  You'll use them all, so make as many widths as you can think of.

When it comes time to hem, take out the appropriate width template, bring it down to the edge of your fabric, fold it over the template and press away.  You can use steam and everything.  The cardstock gives you a nice, crisp fold and since you already measured your template when you made them, you won't have to measure the hem again.

Thank yall so much for your advice.  Im going to start another dress with a straighter skirt today so I'll be hemming again soon LOL.  I don't have a serger yet and so Im on a regular machine....and honestly I want to learn how to make a nice hem w/o the serger first just out of stubbornness lol My grandmother (and heck lots of ppl) can do it so I know I can too, I just get flustered I guess when I did so well on the rest of the dress and then the hem looks so awful:(  I did make the hem on the poodle skirt pretty wide so maybe that was my trouble I kept ending up with lots of extraish fabric even though I pinned it down excessively when I ironed it.  It was just a costume so I ended up just blending it in and figured noone really would notice and if they did they didn't say anything.  But I want to get better at it.  Thank you guys again!