This is my life

I'm fairly new to gif-making myself, but I could share what I've learned so far? I'm on Windows 8 and I use VLC media player, Microsoft Powerpoint and Photoshop CS3. (I recommend Easy GIF Animator as an alternative to Photoshop).

1) Take screencaps.
i) You'll want a DVD or a file for this. Open it up in VLC, find your gif subject.
ii) Go to View -> Advanced Controls. A toolbar should pop up underneath the video and the last option is Frame by frame.
iii) Put your video in fullscreen view [*a], take a screencap (Print Screen/prt sc key on your keyboard). Print-screening saves the image to your Clipboard, so you need to retrieve it. Open up Microsoft Powerpoint, create a load of blank slides [*b], ready to paste images into them. Once you've pasted you can right-click on the image and Save as Picture. Create a new folder just for the gif so you don't lose anything and save the images with sequential numbers for filenames.
iv) In VLC, Click Frame by frame, then take a screencap, Frame by frame, screencap. Repeat until you have your full gif movement.[*c]

In Photoshop:
2) File -> Scripts -> Load Files into Stack -> select screencaps (this is where it helps to have them all in one folder) -> Ok -> Ok. Wait for the script to do its thing. Once all the files are loaded, move onto Step 3)
3) Window -> tick Animation. If a timeline appears, go to the bottom right hand corner of the Animation window and select 'Convert to frame animation'.
4) Right hand side of Animation window, just under the x to close there's a drop down menu -> Make Frames from Layers
5) Right hand side of Animation window, drop down menu -> Reverse Frames (I don't know why, usually they import backwards, run the gif to check.)
6) To resize to either width 250px or 500px: Image -> Image Size -> Ok (it'll apply to all frames automatically)
7) For colour correction, Layer -> New Adjustment Layer -> Curves (or Brightness/Contrast, or Levels, or Colour Balance. Play around with these, see what works.)
8) Make sure looping Forever is selected. Sort the time delays for each frame.[*d] I usually start with 0.08 seconds and then adjust incrementally faster or slower depending on what looks good.
9) Add any text you want[*e]
10) File -> Save for Web and Devices[*f] -> Save

a You could not go fullscreen, but I find that having a larger image initially improves overall quality. If you don't want the added hassle of fullscreening and pasting into Powerpoint, in VLC you can use Video -> Take Snapshot, which will automatically save the file to your Pictures folder with dimensions 720x404 pixels.
b I do this because it means I can scroll through the frames as I'm collecting them and see how it's shaping up. It allows me to check before I save the images that I'm not duplicating or missing out a frame, because with all the repetition of capping and moving forward a frame it's easy to forget where you are. If you miss out a frame and you don't realise until everything's in Photoshop, you'll have a jump in your gif and it's really hard to find the right timestamp again.
c You can have about 30 frames (with the image sized at 250 pixel width) or 15 frames at 500 pixel width before the filesize becomes unwieldy. There's no 1MB limit on Tumblr anymore, but anything approaching/above 2MB you're risking the gif freezing and staying stuck on upload, even if it worked in your browser beforehand.
d To apply the same delay for all the frames in a range, click on the first frame, hold shift, click on the last frame, and all those between will be selected. Then type in the time just once.
e For black/white/yellow border around text to help it stand out, double click on the text layer until you get Layer Options, then tick Stroke, click on Stroke to set colour/width etc.
f If you have a lot of frames and your filesize looks quite large, in the Save for Web and Devices menu there's a Colors option which allows you to decrease the number of colours used in the gif and reduce the filesize.