I understand the concept of Oracle. But I have several questions need your help:

1. Should we create primary key for almost every table?

Oracle will automatically create a unique index with the creation of a primary key on the table. If i do not need index on this column should i create this primary key? I remember that unique index is not easy to maintain. Is that correct?

2. In a table creation script should i specify the storage,
such as initial, next? Or should i just use the tablespace
default storage?
For some special table I will spesify at table level.

3. Should i create the foreign key for every related table?
The foreign key will affect the exp/imp.

I have no idea about what the best way to create schema.
Every help is appreciated.