In which pH range are silica-based TLC plates stable?
Assuming "normal" TLC with silica as stationary phase, and a mix of ethyl acetate / hexane as eluent, charged compounds (i.e., salts) do not elute well; their adsorption is too tight to move forward.

Hence, if your reaction is performed under acidic conditions (sulfonation reaction, for example), drop a small sample of your reaction into a test tube or small vial, gently quench it against an aqeuous solution of $\ce{Na2CO3}$, extract it with some ether / MTBE / methylene chloride (well...) and spot the extract on the TLC plate.  With some training, this works easily around o.5 mL of total volume.

Conversely, if your reaction proceeds under basic conditions (like a Grignard reaction, for example), bring the sample back to neutral, for example with dilute HCl (or, with more fragile products like tertiary alcohols, with an aqueous solution of $\ce{NH4Cl}$), and then spot the organic extract on the plate.



I referred to "normal" TLC as there are other stationary phases than silica, too.  Alumina (basic, neutral, acidic) works with the same principle as silica.  These two contrast to applications of RP-TLC, were the stationary phase is coated with alkyl chains, and much more polar solvents are deployed as eluents, hence with much lesser issues of free salts / free acids. But the price tag for these plates is higher than for normal phase TLC.