Tuilagi was cited for a tip tackle on scrum-half Danny Care two minutes into Leicester's Aviva Premiership final defeat to Harlequins on Saturday. The Tigers centre was cleared at a disciplinary hearing on Tuesday night after England lawyer Richard QC successfully proved that Care's knee had hit the ground before his torso.
"I have had a one-to-one with every member of the touring party. I had a good conversation with Manu on the strengths of his game and the areas we need to make sure he is on top of," Lancaster said. "Part of that is tackle technique and discipline. He understands that. He is a young player and still getting experience."
The independent disciplinary panel backed referee Wayne Barnes, who penalised Tuilagi for the tackle but ruled the tackle was "not dangerous". It could have been worse for Tuilagi given the International Rugby Board's clamp down on dangerous tackles.
"I was relieved. There was a concern," Lancaster said. "I am pleased to see the people in charge found it was dealt with on the pitch at the time. I am delighted he is available."
Lancaster has extended the warning to the whole of his squad ahead of their three-Test series against the Springboks.
"The directive is clear and players are working hard to abide to that," Lancaster said.
"It is a difficult one, an 11-stone scrum-half comes running at a 17-stone bloke. Danny said the force of the impact took him off his feet.
"People recognise Manu's intention was not to hurt anyone.
"We all understand the reason the rule is there. Players just need to be careful if you are picking somebody up. When we do video sessions we will highlight areas of 'red flag' - things such as the directives around the breakdown, competing for the ball when the referee calls ruck, being onside and tip tackles."