I go by several factors. I look into what they are targeting, what sector, what the rumored acquisition is and see what I can find out about that company and if others have already done all the DD then great but other times you just have to search for it yourself like what their expected growth is looking like etc..
Another key factor is who is behind the SPAC, a trusted name, someone who has brought successful SPACs to the table. All of that is important. But the sector is one of the biggest factors..