Things to.look for are largely personal preference, but they include things like the layout (ANSI, ISO, JIS, DVORAK, COLEMAK…), switch (linear, tactile, clicky, silenced and their weights), board size (40%, 60%, 75%, TKL), case (milled acrylic, sandwiched layers, milled aliminium, wood), case colour, programmability, lighting (yes/no, static colour, RGB, per key colour setting, underglow…), modability (plug in mods, soldering, hot swap switches and so on), key plastic (ABS, PBT, POM), key legend style (pad printed, dye sub, double shot, shine through, blank), key colour and colour schemes. Oh and cables.
Pretty much any aspect of the vaord can me modified to your taste.
The easiest and most instantly gratifying is key caps. I like colourful, blank PBT but also have more normal lettered keys on other boards.