What are the best and safest solid foods for babies?

Depends... Depends on age and other factors. In general, pureed vegetables and cereals come before meats and dairy (other than breast or formula); single ingredients before mixed; no-no's include: chunks (choking hazard), honey (botulism), eggs/fish/seafood (more allergenic), salt and sugar (addictive), and juices (juice is a fruit from which all good stuff has been removed.).
Small bites, purees. Once your child is chewing food, make sure you cut it into bites small enough that they cannot choke on them. Also make sure that they chew and swallow their bite before putting more food in their mouth. When your child doesn't have many teeth and isn't chewing pureed and soft foods are the safest. And remember, no honey before age 1!