I don't understand the difference between Direct and Indirect Object Pronouns - how do I use them?

A normal Direct Object Pronoun (DOP) sentence would look like this:

--> J'attends le bus pendant deux heures chaque matin.

--> to change this sentences into the DOP form we replace the object (''le') with the following pronouns:

SINGULAR: me (m') ; te (t') ; le/la (l') ;

PLURAL: nous ; vous ; les ;

So J'attends le bus pendant deux heures chaque matin becomes je l'attends pendant deux heures chaque matin.

Most commonly the key difference between a direct and indirect object pronoun is that an indirect object pronoun (IOP) is preceded by the preposition 'à'. 

--> Ma mère a donné ses bijoux à ma sœur.

--> to change this sentences into the IOP form we replace the object (''à ma sœur') with the following pronouns:

SINGULAR: me (m') ; te (t') ; lui ;

PLURAL: nous ; vous ; leur ;

--> So 'Ma mère a donné ses bijoux à ma sœur' becomes 'Ma mère lui a donné ses bijoux'

There are several important things to remember:

1. The sentence order for IOPs and DOPs stays the same : SUBJECT -- IOP/DOP -- VERB -- OBJECT

2. When translating from English, sentences can be misleading. eg. téléphoner = to call someone NOT to call to someone --> but in French 'téléphoner à ' takes an Indirect Object Pronoun

3. 'lui' and 'leur' do not change according to gender.

4. 'nous' and 'vous' look the same in Indirect and Direct Object forms --> here it is necessary to take an educated guess based on the verb.  --> Common verbs taking Indirect Object Pronouns: téléphoner à; donner à; dire à; demander à; permettre à; promettre à; répondre à; obéir à;