mRNA and initiation factors bind to small subunit of ribosome; in prokaryotes, the ribosome binds to the Shine-Dalgarno sequence and in eukaryotes, ribosomes bind to 5' cap. In both cases, the places where the ribosome binds are in the 5'UTR region of the mRNA. Next, the initiation complex (which already includes a tRNA-Met (initiator tRNA) scans in the 3' direction for a start codon. Once found, tRNA-Met (iniator tRNA) binds to AUG codon at P site...in which all subsequent binding are at the A site. Lastly, the Large ribosomal subunit sits on top of everything like a hamburger and binds to the initiation complex. **Basically, it goes: initiation factors --> small subunit/tRNA-met --> scanning --> large subunit.