How to Learn to Swim if You Always Sink

My List of Techniques for Motivating Yourself/Fighting Procrastination

Not every technique works in every situation, but I've found usually one or more of them will.

If you don't have a list of things to do, make one. Maybe mark a couple things as the top priorities.
Read over your task list. You don't have to do any of them, just read them so they're "top of mind".
"Get eyes on it." E.g. if you've been meaning to work on something, maybe there's a document that you would look at to get you started, like an email where the thing was discussed. It can be helpful to just look at that document even briefly. You're not committing to actually do any work, just take a look.
Clean your room/house/workspace/whatever. It might not logically be your top priority, but I find that clutter can be a sort of mental block. It can also be a mental block if you're in some sense "being too lazy", e.g. lounging on your couch in your pajamas vs. sitting at your desk, or if there is something else wrong with your environment (temperature, noise, etc.)
Decomposing tasks into smaller tasks is frequently useful. You can do this with just about anything, even to an absurd degree. E.g. if you want to lose weight, you could write down "google how to lose weight" on your todo list, then literally type that into google, cross it off your list, close the browser tab, and take no further action, and it would actually be productive.
Keeping good documentation makes tasks way easier. For example, if you're a programmer and need to make a change to a system you haven't touched in a while, it's far far easier if the system is well-organized and documented. If it's not, you may be able to get some motivational energy out of resolving to improve the docs while you do the task. One thing that has made a huge difference at various points in my career is drawing /diagrams/ so I know what is connected to what. This removes a lot of the frustration that can arise when trying to (re)acquire understanding of a system. Instead of everything becoming a sort of "fishing expedition" to even get oriented, you just look at the diagram. Docs aren't limited to programming though. You can have a written SOP for any recurring task and it may make the task easier.
Mark Forster's AutoFocus system.
"Speed date your tasks." Make a list of them and cycle through them, a few minutes on each. This is sort of a special case technique when you have several things that all feel important.
Generally speaking, I believe that compulsive/addictive habits (e.g. surfing the internet, playing video games) result in lower productivity. The mechanism, I think, is sort of like the concept of "empty calories". The brain wants a certain amount of stimulus. It can get it either from doing productive activities (good calories) or unproductive ones (empty calories). If you do too much of the latter, the brain won't be interested in doing the former because it already met its stimulus budget.
If you don't feel like doing a certain task, you can always just do something else as long as it doesn't fall into that compulsive/addictive category. For instance, you could take a walk or get a snack.
If you were previously hard at work on one project and now need to switch and ramp up on a new one, you may need some "mental downtime", as much as a day or more. During this time you just try to relax and rest, but again ideally you want to avoid the addictive stuff.
You may just need to sleep. Nothing wrong with taking a nap!
It can be helpful to just sit and literally do nothing until you're bored. May be more useful if coupled with meditation, because if you sit and get lost in negative trains of thought, it may be counterproductive
You might have hit your productivity limit for the day and should just give up until tomorrow.
If you are really stuck, it could be helpful to journal about why you think that is. Is there something else on your mind that ought to be dealt with first? Are you sure the task really matters? Can you delay it? Can you pay someone to do it? Can you just not do it at all? What would be the consequences? Would they really be so bad? What would you rather be doing? Etc.
Sometimes people say "just work on it for X minutes". I would modify this to "set a timer for X minutes and resolve to either work on the thing or do nothing at all". Lower pressure is better.
Just keep "knocking on the door". E.g. if you don't want to do your top priority task X, maybe just do a different task, but remember to ask yourself later (perhaps when you're in between activities) whether you feel in the mood to work on X.

Maybe worth mentioning something I don't think works very well: making deals with yourself, e.g. if I study for an hour I get to watch TV for an hour. This point is a little subtle, because I do think it can be reasonable and helpful to have a plan along the lines of "study for an hour then watch TV for an hour". But you want to be studying because you believe studying advances your goals, not to obtain the TV watching time. If you're truly relying on that dangling carrot to motivate you, there's really nothing stopping you from skipping the studying and watching TV, which is an easier means of achieving the same end. Moreover, if you want to watch TV that badly, it can become a distraction as you try to study. Plus you get an undesirable coupling between the two things: if you don't study but watch TV, you may feel guilty, and if you study but don't watch TV, you may feel "robbed of your reward". That might even lead you to watch TV when you weren't even that interested in it!

The case where "study for an hour then TV for an hour" makes sense is when it is more of a question of scheduling: you don't have a lot of trouble motivating yourself to study, nor do you feel you are watching too much TV. Your plan is merely a case of planning out your day, which makes sense.