When the item can stand heat, a hot air gun is my goto for removing any label. It will also allow removing years old, dried masking tape in only a few pieces. I avoid scrapers, except maybe my fingernail or a plastic razor blade.
The latter is becoming more common. It used to be a specialty item in boat stores to allow scraping fiberglass gel coats without scratches.
Once the label is off, then comes the goo. To much heat leaves more goo. For goo, one can often remove it with another piece of tape. Masking tape works well. Others do too.
For solvents, butter is probably the mildest. It has surfactants that WD-40 doesn't. My next strongest solvent is VM&P Naphtha (mostly low boiling hydrocarbons). I will often add about 10% toluene or xylene to up its potency. After that, I would (past tense) usually go to MEK. MEK is an aggressive solvent and is not suitable for anything with paint or plastics. Be aware that there are some adhesives that are virtually immune to the above, but readily removed with alcohols. An example is one of the Form-A-Gasket products, which is designed to be insoluble in petroleum solvent.
More recently, I have moved from a series of MEK to cellosolves. Butyl cellosolve + a little "saponifier" (e.g., ethanolamine) + water works wonders. Without water, that combo is quite aggressive and attacks enamel paint. With water (70% to 90% or more water) it is a great cleaner and doesn't attack cured enamel. Many versions of that mixture are available in household products and usually have added surfactants, which helps.