Yes, there are many things Hillary Clinton could have done to win the election, but the number one thing was better running mate. She could have picked a better running mate. She picked the wrong running mate. Your running mate needs to be someone who covers your weaknesses and he didn't. She needed a running mate who could get minorities and millennials out to the polls to support her.
Hindsight is 20/20. If Trump had run a "traditional" campaign, he might have lost. If Clinton had run a different campaign, or if there were no email hacks or no Comey who knows what would have happened. Hopefully the Democrats will learn from this and make changes for the future.
Where Hilary fell short this election was clearly in the swing states, which she won very few of. To have won, she really needed some of the midwest states like Wisconsin and Michigan. She didn't give them the attention they needed despite the evidence that she wasn't as popular there as she needed. In the primaries she was not popular in either of those states, and even though she was predicted to win, she fell short. She also needed to targets the middle class and upper middle class more. Out-polls said that she didn't target them enough and so Trump became more appealing.
Hillary Clinton could not have won the election if she ran her campaign differently. What could she have done differently? Tell the truth for a change? The reality is that her loss is emblematic of a country that is sick of liberal politics as usual. Her side has done nothing to better the average voter's lives.