I'll try to explain about the Glycemic Index (GI) as I feel like I'm starting to become an expert!
It's basically an index of foods where food is given a rating. The rating stands for how quickly the food makes your blood sugar rise. A rating of over about 70 is high, or quick acting. Some sugars are around 100, mashed potato is around 95, rice cakes are also very high, cornflakes are high, surprisingly melon is also in the 90s....55 to 70 (or thereabouts) are moderates. Your blood sugar will rise a bit more slowly than high. Then, below 55 is low which is what we want to mostly aim for (it raises your blood sugar more slowly and keeps it more level). Foods here are lentils, beans, some fruits such as cherries and apples, oat based foods etc. Meat, salad etc is 0 so has no affect. If you really want to eat a high GI food such as a baked potato, team it with a low GI food such as baked beans. This will make it a moderate affect on your blood sugar. You can look on the net or buy a book which shows you food values - I have a book that has a huge list of food and I find it very useful. I am so surprised sometimes at some food - a mars bar is 55 on the rating so is quite low, but as it contains so much sugar it's still probably not the best thing to eat. Parsnips are also very high - in the 90s! It can be very baffling at first, but I have found it really has helped my blood sugars. Fat in foods seems to bring down the GI of foods, but we obviously want a healthy diet so it's not best to eat a lot of fatty foods! And fat-free products seem to pack in a lot of sugar (such as fat-free yoghurts, unless they use sweeteners) so you just have to be aware when you make your choices.
I've also heard a lot about how bad aspartame is, and it seems to be in so many things I buy from diet drinks (including sparkling water) to yoghurts. I've actually heard that it can cause problems with your brain, and that the verdict is still out on splenda. Someone on this forum has suggested using stevia but I've never tried this.
I hope this helps and isn't too confusing!