How to know if a chemical is a strong base, strong acid, weak base, weak acid

Please help me :)

Also how would I know if a chemical is a SALT OF A WEAK BASE and a SALT OF WEAK ACID.

Please explain and give examples. :)
THANKS IN ADVANCE! :)

How to know if a chemical is a strong base, strong acid, weak base, weak acid?
Let's start by saying acids are proton donors [ie form H+] whereas bases are proton acceptors.
examples
HCl + H2O ---> H3O+ + Cl- ... so acid
NH3 + H+ ----> NH4+ .... so a base

While to a large extent experience in chemistry will guide you which is which, the only true way is to check the dissociation constant to find out if the are strong or weak. This will tell you whether they readily break up [dissociate] or not.
examples
H2SO4 ---> 2H+ + SO4 2- strong acid
CH3COOH <--> CH3COO- + H+ weak acid, note the reversible sign to indicate it only partially dissociates.

Also how would I know if a chemical is a SALT OF A WEAK BASE and a SALT OF WEAK ACID.
Here you have to look at the two bits in the salt and see which acid and base they are formed from.
Remember the key equation ACID + BASE = SALT + WATER

Example NaCl would have to be made from NaOH and HCl both of these are strong acid & base
but
NaCN sodium cyanide is a salt of NaOH strong base and HCN a weak acid
in solution in water, the strong one 'wins' so it will be alkaline
NH4Cl ammonium chloride is a salt of NH3, ammonia, weak base and HCl hydrochloric acid a strong acid. So this one has a pH less than 7 ie is acidic

Well, first Universal indicator paper shows the pH of the substance. This will then tell you on a scale of 1-14 how acidic/alkaline the substance is.
Also, strong bases and acids are usually better conductors of electricity because they contain more (OH-) and (H+) ions respectively.