An author has an h-index of n if they have published n papers that have each been cited at least n times. There are several strategies that researchers can use to increase their h-index, including collaborate with more experienced or established researchers, publish in high-impact and reputable journals, cite the work of others in your field, publish both conference and journal papers on the same topic, continue producing high-quality and impactful research, share your work freely and openly and promote and publicize your work through social media, conferences, and other channels.
As noted by Dr Wolfgang R. Dick , this topic has been discussed previously and I said then and again say now that I find the best way is to meet people at conferences and discuss areas of mutual research interest but they might need a long time until they get their work published so your h-index will only take a while to increase. As such, I expect my h-index to increase by no more than 1 per year at most.