General

If my thoughts are really bad, I'll tire myself as much as possible mentally.
I'll make myself busy enough in the day so that I won't have the time to even pause and dwell on stupid things.
Sooner or later having a packed schedule will be too much for my body so i'll start distracting myself with games/shows/books/music etc.
Mmm..
I continue this cycle or change it depending on how frequent my negative thoughts are.
I have a system of my own.

Meditate, yoga, lift, walk, run. Breathing deep with yoga/meditation especially clears the mind, makes you feel good/happy, and in the long run it'll help you cope with unwanted situations.

Exercise and meditate. That has helped me with my thoughts

You can't.

Personally I either just marinate in them by myself or I distract myself. I'm thankfully mostly busy with a bunch of small things occupying me so I don't dwell on negative thoughts as much anymore as I used to. Married life definitely improved that

Counselling helps.

By doing something else to distract myself while not dwelling

you think even more negative thoughts cause two negatives make a positive

I usually sleep it off. Lately I've been distracting myself watching portlandia on netflix cuz it's a funny, plotless show and I dont need to be invested to enjoy it so it's easy to go numb and get a laugh out of it

[url=http://www.basilmarket.com/MapleStory-hellksing-Story-18912.html]Worked for me[/url]

^^ yeah i'd try out mindfulness too it can be helpful. there are some where you can listen to beach sounds and whatnot too.
personally tho it sometimes induces my anxiety bc i'm not so good at it

[url=http://en.wikipedia.org/wiki/Mindfulness#Mindfulness_meditation]this but not with any fancy sitting position or anything. I just focus on my breathing.[/url]

Corgis. Lots and lots of corgis.

Alcohol.