Troubleshooting PCR Steps
I think 30 cycle PCR is maximum to see bands by electrophoresis in most of cases, because under the ideal efficiency, one copy could be detectable by 34 cycles of PCR. However, if your expected products are longer than 1 kbp, you might extend several cycles.

I usually add DMSO 5% in any PCR reaction. In my experience, DMSO would not interfere PCR reaction--you can amplify your fragments without DMSO; you could get PCR products with DMSO. Betaine sometimes work better than DMSO, so I am shifting my default reaction mix from 5%DMSO to 5%DMSO and 0.5M betaine. 

For annealing temp, you can not tell which is better, lower or higher than the first trial which showed nothing. When increasing the annealing temp, primers may be able to access your target sequence more and you could get efficient amplification. So you might want to try both. If you have a PCR machine set various temperatures at once by gradient. You could include lower and higher temp together.

Alternatively, I sometimes use the touch-down method. You do not need to determine the best annealing temp in this case. If you just want amplified products, this could be a quick solution. 

Additionally, hot start is also my default condition, because this could not ruin PCR reaction without hot start.

Basically, I change annealing temp. If I do not get good amplification and specificity, I change PCR enzymes. Changing PCR enzymes could mean changing buffer conditions because companies try to give unique features for their products.