In general, Trump was not good on his counter-punching and let too many opportunities to seize the offensive go by.
In the first segment on jobs, when Hillary compared Trump getting a loan from his father with her own father's manual work, Donald should have shot back "I earn my money every day in the private sector. You have lived off the taxpayers for 30 years."
In answer to requests for Trump's tax returns, ask for info on who actually paid for Bills and Hillary's speeches. Often the name is a front group like a trade association. We should know who really controls the IOUs for the money.
After a few minutes on the tax returns, Trump proposed releasing them if Hillary releases her deleted e-mails. Then, Hillary said the emails were a mistake. Trump closed in for the kill and said it was more than a mistake, it was corruption and then, before anyone else said anything, he abruptly switched back to his tax returns and debt structure, going from a winning to a losing issue voluntarily. That opened the door to many minutes on this no win topic.
Hillary derided Trump's business practices saying he stiffed workers and contractors and went bankrupt. Trump could have answered: "I work in the private sector and take my chances. Sometimes I win, sometimes I don't. You don't have that problem. You can just raise taxes. Or borrow the money. You've never been in the private sector and you don't know what it is like to have to meet a payroll and face that pressure."
At the opening of the race discussion Hillary said a person's geographic location determined the quality of education their child gets. Trump could have hit her on her opposition to school choice (she is for public school choice only) linking it to school segregation and comparing to the all-white academies set up in the south in the wake of the Brown decision.
In the race segment, Hillary bemoaned the fate of young black men stuck in prison for years for nonviolent drug offenses. Trump could have pointed out that the reason they were locked up for mandatory sentences is her husband's and her anti-crime bill of 1994 that required states to use mandatory sentencing to become eligible for federal Law Enforcement Assistance Act (LEAA) funding.
On the 1973 anti-discrimination lawsuit, Donald should say that he was only 28 and it was not his company to run. It was his father's and not his decision to make.
Further, Donald should have stats on the % of his HQ labor force that is minority and the % of those making more than $100K that are and compare it with the state department and/or the Clinton Foundation.
In response to Hillary's comments on cyber security, Donald might have discussed her private server and its vulnerability to hacking. This is like being lectured on bank security by Bonnie and Clyde.
In distinguishing positions on the Iraq War, Donald should quote his 02 statement and then quote his subsequent statements and make the point that she voted for the war at the same time that he was speaking against it.
Responding to the accusations about his quotes on women, Trump might cite Hillary's Gestapo like tactics in going after the women linked to Bill, not to deter them or to get a divorce, but to cow them into silence so her husband could be elected president.