- Thaw one aliquot of DH5α competent cells (from –80°C freezer) on ice  
- Add 1-5 μl DNA and 75 μl competent cells to new cell culture tube. Do not mix the cells by pipetting. Just tap the tube gently  
- Incubate on ice for 30 minutes  
- Heat shock in 42°C water bath for exactly 30 seconds. Do not mix or shake.  
- Cool on ice  
- Add 900 μl liquid media (e.g. LB) to cell culture tube  
- Shake at 37°C for 40-60 minutes  
- Centrifuge at 5000 rpm for 2 minutes  
- Remove all but 100-150 μl of the LB and resuspend pellet  
- Spread 100-150 μl on plate of media + antibiotic (e.g. LB agar + carb)  
- Incubate plates up-side-down, overnight at 37°C