I also know that attempting to enter the 'clean vs. restore vs. argon chamber' debate a few posts in to my very first blog is a reflection of great intelligence. So without delay.
First question: Is it absolutely, irrevocably, unassailably a common product or item? No special marking, patent, tag, cave drawing, double stamp, upside down bi-plane, FDR bitemark, rare earth metal or stone? If you are not 100% sure, my humble suggestion would be you treat it as valuable. There are lots of variations in some common older tools that can take them from ho-hum to special. This is especially true as you get into pre-1900 items. Do your research, and proceed slowly.
If its common tool destined for your bench (and god forbid, within your Queens reach too) - have at ye. My personal favorite is electrolysis to remove rust from larger ferrous items, its painless and completely foolproof when setup properly, and also has the side benefit of softenting old japanning if you're stripping a metal bench plane. Do read the safety info online, do it outside, do use a GFC on the circuit, don't use stainless steel, don't lick the damn thing while its on - basically, dont be an a-hole and get Sawstop involved with my water bucket.
For these projects, Sandflex blocks, made by Klingspor are outstanding for smaller items and light spot rust. Use only the fine and medium, coarse is for restoring 1/2 ton truck panels. I almost always start with the fine, and work up to Med if I have issues, then back down. Very very light rust can be resolved or at least stopped with a proper coating of Rennaisance Wax, which you should use on everything but your dog and mother. All of these methods are abrasive to some extent (even R. wax has polishing compounds), so proceed carefully.
Electrolysis is more gentle, but requires more setup, and can be challenging where un-removable parts exist that would not fare well with the waterboarding shock treatment. You can coat those parts in wax, but are you here to work the wood or fully restore old tools we've already established are not worth bird farts? Your Call.
OK, so we've covered what you can do with the gloves off - what about for the prime stuff? Lee Richmond of The Best Things rule is the best I've heard, due to its simplicity.
'Do nothing you can't un-do'Essentially, wipe down lightly with clean cotton or soft microfiber, wax with a musuem quality wax, lightly buff. Done.
Boiled Linseed Oil should really only be used as a last resort, and I struggle with this one. When dealing with wood planes, especially coming from some regions of the midwest (tragically - Sanduksy planes) - these things can be like the desert. Some valuable tools are so parched that an oiling is required to keep them from checking/splitting into oblivion. But it can greatly darken the wood over time, and has been avoided by dealers, collectors and museums for some time now.
So the question becomes, is the tool more valuable in its current parched state, than it will be after the oiling and potential darkening? It alot of cases, its best to just leave it for the shelf, give it a good coat of wax, and protect it from the environment as best as possible. You cant undo BLO - you can undo wax. If you guys know of any museum quality 'reconditioning' type solutions being used other than a BLO/Tung oil, please let me know.
What about rust on the blade, you say? You want to use it? Well - remember, its the patina that makes collectors and dealers tingle like schoolgirls at a winter formal. Big rust should probably be addressed I cover a piece of paper in duct tape, cut out a hole the size of the rust spoty, tape over the item. Hit it with the rust sponge. Most of the rust removed, without destroying all the patina. flat a bit of the back, hone the edge, wax the rest. Don't lap the sides, bottom, top, strippers, santa or anything else.
Thats about it - the best advice I can give you is the 'ounce of prevention'. Try to search multiple online antique dealers before you buy a rust-bucket. There's so many good users out there for cheap, I just wouldn't split hairs and buy a real dog. And I say this as a humble man who proudly snapped up a real bruiser bedrock off ebay and then watched Patrick Leach sell a near-mint one for $22 bucks more.
As its been said; not in my house. Anymore.