Here in the UK we have the needle exchange program.

I go in once every 6 months, pick up needles/barrels/wipes/disposal boxes then drop off my full up disposal boxes, give the heroin addicts a cheeky bicep flex as I walk out the door and crack on with my day.

My empty protein jug, a 5 lb protein jug holds a lot of pins. Then I tape the lid tight, double bag it and chuck it in with the rest of the trash..

i put all my pins in a water bottle and spray some great stuff ( the foam that expands at home depot for cracks and what not) and itll be a sealed foam bottle so no one will get pricked by a pin....and the plastics i just toss them in a recycling bin...never had a problem

I throw mine in my neighbor's yard all winter. That way when spring rolls around he'll think twice about being the first to mow, just to make my yard look like shit.

(I'll put em in empty detergent bottle and toss it in the trash when full.)

Baby wipes container.

Always throw all my shit away in an empty bleach or laundry detergent bottle because they're hard plastic. I just let it accumulate throughout the month and when it gets full just close it shut and trash it.

I collect them

One of them dar Cell tech jugs.

A sharps container or you can make your own, by using a similar receptacle (thicker plastic). Some solid examples below.
As far as fire goes, I supposed it depends on where you live. If I lighted a fire in my yard, the fire department would be there in minutes.

I get small sharps containers at the pharmacy for 3-4 bucks. Than seal them and hide the in the trash. It's completely safe and legal where I live. It's worth asking for the pharmacy.

I like to shove three or four into an empty pop can or energy drink can, then I fold the edges down and toss them in to the trash. this way no one gets pricked and no one is the wiser.

I throw slin pins and needles in a sharps container. The syringe without needle I just toss in the trash.

I have a wood stove/boiler that gets crazy hot. I incinerate all my old pins and vials.

Good ideas below....i have used an Ensure bottle, milk jug (too thin, really), beer bottle (it will go in), while breaking the needle off with the cap. I burned some vials and syringe once. I like the trash better.

I leave all my needles exposed after using them and toss them in the can. Hoping some unsuspecting asshole digs in my trash and gets stuck by one.

I use a laundry detergent bottle. When it's full I throw it a random dumpster.

Google: disposing of syringes and needles in your state

In my state syringes and needles can be disposed of in the garbage if the they are placed in a puncture resistant container such as a Polyethylene terephthalate (PET) bottle (e.g. 2 liter soda, Clorox, or radiator fluid bottle) with a tight fitting or taped lid and labeled "SHARPS, DO NOT RECYCLE."

I use an empty 5lb thing of protein. It always works out perfect to when the one I'm using for my shakes gets empty the one for my pins is full. I then duck tape the top closed and toss it in my dumpster.

Don't forget about fire! I have a fire outside at least once a week. It gives me a chance to get rid of just about everything i don't want to fall into the wrong hands

Buy a sharps container. Drop it off at the pharmacy when it's full. No questions asked they dispose of it for you

Ok so they sell disposal containers but most are meant for slin pins or like .8ml prefilled syringes so like they hold 3 months or 90 pins at one a day...but 3mls they hold like 30 Max and they cost like $5-10 each so a cycle may cost $30 to dispose of using the containers...so I recomend milk jugs or better yet thick juice containers with a lid like juicy juice containers