You can determine the sign of ΔH, ΔS, ΔG by understanding the reaction or process.

If a process or reaction is exothermic, ΔH is negative. If a process or reaction is endothermic, ΔH is positive.

If a process or reaction is become more ordered, ΔS is negative. If a process or reaction is becoming more random, ΔS is positive.

If a process or reaction is spontaneous, ΔG is negative. If a process or reaction is nonspontaneous, ΔG is positive.