I second Jack’s recommendations – really good advice. I find that having a continuing narrative with characters that I follow really increases my interest level. I have also found that I really enjoy recording my characters’ adventures on my blog (https://warwellwg.blogspot.com/).
I also find it helpful to use fast playing rules. A set of rules that works fine for 2 or more players can really bog down playing solo because your army management tasks have doubled. This is especially true if there is record-keeping or card hand management. Each person has their own preferences as far as this goes so my only advice is to experiment and find what works for you.
Finally, one benefit to solo gaming is that you can play around with rules, genres, etc. that others may find a bit odd for their tastes.