A thrifters guide
I've popped this in off topic as it technically can apply to anything from Cameras to the humble toaster, for a long time I've operated by these rules for many of the collections I have and hopefully it'll help somone else, I'll stick to photography kit as the example here.
Before you start searching do a spot of basic learning, stuff like behaviours (Many FSU's can be damaged by changing speed before cocking shutter etc) what damage looks like, i.e fungal growth, corrosion and metal fatigue.
You don't have to be an expert but a little knowledge will save you from buying a potential paperweight.
HandyTools to have in your arsenal are presicion screwdrivers, electrical contact cleaner, thin oil, high grade wet and dry paper, degreaser (lighter fluid is good but may not be purchasable by younger members) and appropiate lens cleaning cloths.
Also handy to carry when searching is a swiss army style tool (I use a Custom Victorinox huntsman with a micro screwdriver added), a bright LED torch (In the UK Rolson ones can be found dirt cheap), a small coin like a 20p or 25 cent coin and of course comfy shoes.
Car Boot sales/ Flea markets:
This is where often the biggest bargins can be found but also has the biggest risk as theres no real come back, its sold as seen.
Bring a buddy, 2 sets of eyes are always better than one, they can also help you check focus alignment or hold things while you check kit.
Don't be afraid to talk to the seller, be friendly even if they seem like a grade A A-hole and never be afraid to barter, do they take what they say with a pinch of salt (The amount of times I've been told a junk item is a collectors piece).
Plan your visits too, some are real early and others like to sit in the afternoon, get there early to try and find the good stuff but don't be afraid to swing by at the end for a bargin as the seller doesn't want to lug it home again.
Charity Shops/ Thrift stores:
Go mid week if you can, donations are typically dropped off on weekends as this is peoples day off and it allows a day or two for them to sort it.
Don't be afraid to barter, might seem odd in a shop enviorment but I've had chunks knocked off of stuff, get to know the staff too, they may alert you to things before they go out on the floor.
Make sure you dig in baskets, smaller cameras and accessories often get put in bric-a-brac bins.
Junk shop/ house clearence shop:
These are a little different to the above, usually they trawl estate sales or the car boots/ Flea markets and buy in bulk to fill out their stock.
Talk to the staff as often theres a lot in back, again barter too to get a good price.
Pawn shop/ Second hand store:
You wont just find red spherical rings here, you can find some real bargin kit and I've even seen on occasion higher end stuff appear.
Here in the UK we have chain ones like Cash Converters and CEX, they generally won't budge on price but you do have the ability to return here and get credit with trade ins to get money off.
Most shop staff will allow you to fully test stuff and can sometimes be persuaded to alert you if something comes in.
Last but not least on the physical side, the Camera Store:
These fabled beasts do still exist although rare in the wild, their kit if the shop is worth their salt will always be tested properly and carry some level of guarentee, whilst prices may be fixed they may offer to do bundle deals or even knock a little off if you are a frequent buyer.
Other similar store types have helped me with parts so its possible with these too (somone else might be able to share on this).
Stick to paypal or similar and avoid gift payment unless you are able to trust the seller 100% or its cheap enough to allow for the risk.
In most case theres no come backs, its sold as seen and you'll have to take their word for it as you can't physically look at the item before hand however sites like Ebay and Amazon do offer protection if something isn't right.
On a final note don't be afraid of fixer uppers, spares repairs or untested needn't ring alarm bells, as you can see from the many stickies on here it's possible to sort many things however if you aren't comftable with DIY repairs be more weary as paying somone to do some repairs can far out weigh the return.
If you want saving ideas use change jars and if trying to be strict on saving set yourself a fine system, I usually fine myself the value or double of the item I bought, you might scoff at this but I legitamitly used this to buy a BMW M3, also sort through your redundant items and sell or trade them to fill out your budget.
Hopefully this will help some people and please feel free to add tips of your own.
Those aren't left over screws, that's weight reduction.